Archive for the ‘MySQL DBA’ tag
MySQL DropIndexIfExists
In reply to a question about how to conditionally drop an index on a table in MySQL. It appears the syntax doesn’t exist. However, maybe it does and I missed it. If I did miss it, I’m sure somebody will let me know. However, I simply have a dropIndexIfExists stored procedure for this type of database maintenance.
Below is my dropIndexIfExists stored procedure:
-- Conditionally drop the procedure. DROP PROCEDURE IF EXISTS dropIndexIfExists; -- Change the default semicolon delimiter to write a PSM -- (Persistent Stored Module) or stored procedure. DELIMITER $$ -- Create the procedure. CREATE PROCEDURE dropIndexIfExists ( pv_table_name VARCHAR(64) , pv_index_name VARCHAR(64)) BEGIN /* Declare a local variable for the SQL statement. */ DECLARE stmt VARCHAR(1024); /* Set a session variable with two parameter markers. */ SET @SQL := CONCAT('ALTER TABLE ',pv_table_name,'DROP INDEX ',pv_index_name); /* Check if the constraint exists. */ IF EXISTS (SELECT NULL FROM information_schema.statistics s WHERE s.index_schema = database() AND s.table_name = pv_table_name AND s.index_name = pv_index_name) THEN /* Dynamically allocated and run statement. */ PREPARE stmt FROM @SQL; EXECUTE stmt; DEALLOCATE PREPARE stmt; END IF; END; $$ -- Reset the default semicolon delimiter. DELIMITER ; |
You call the procedure like:
CALL dropIndexIfExists('payment','idx_payment01'); |
As always, I hope this helps those looking for a solution.
MySQL and JavaScript
Sometimes students truly amaze me with their curiosity. The question was simple from their perspective while we were discussing MySQL’s builtin string functions. How would you do something like this JavaScript logic without using literals or session variables?
// Declare a string and substring. var myStr = 'Get me from the string.' var mySubstr = 'me' // Assign the substring to variable by rescuing it from the larger string. var rescued = myStr.substring(myStr.indexOf(mySubstr),myStr.indexOf(mySubstr) + mySubstr.length) // Print the result. print(rescued) |
tested with MongoDB, like
mongo --nodb --norc < parsing.js |
returning:
MongoDB shell version v4.0.20 me bye |
They thought the question would show SQL’s limits as a problem solving and programming language because they didn’t see how MySQL could assign a variable for evaluation in the builtin functions.
They were surprised to see how I showed them that they could do it. Since they disallowed session variables, I built a sample table and inserted the string value in a text column before writing a query with a Common Table Expression (CTE).
The MySQL steps are:
-- Stable testing scenario with table values requires a test table. DROP TABLE IF EXISTS sample; CREATE TABLE sample ( text VARCHAR(100) ); -- Insert the literal string into the testing table. INSERT INTO sample ( text ) VALUES ('Get me from the string.'); -- Test using a WITH clause to place a variable in context for use -- in the query, relying on the fact that a Cartesian set of one -- column and row becomes a new column in all rows of the other -- table's set. WITH struct AS (SELECT 'me' AS result) SELECT SUBSTR(text,INSTR(text,struct.result),LENGTH(struct.result)) AS rescued FROM sample CROSS JOIN struct; |
It returns the following:
+---------+ | rescued | +---------+ | me | +---------+ 1 row in set (0.00 sec) |
Wow, SQL works like a programming language was the response of the class. It’s like anything else in technology, new stuff isn’t as cool as old stuff until you learn how to use it.
MySQL SQL Filters
An interesting outcome of teaching SQL is discovering what skills new users require. One that I continuously rediscover is how to build a test case for various elements of SQL. This is a small article on querying with filters in the WHERE
clause.
There are several of the exercises in Alan Beaulieu’s Learning SQL, 3rd Edition that would benefit from example setup. For example, Chapter 4 provides a snapshot of the payment table but doesn’t provide any instructions.
You can create an exercise_4_2 table with the following SQL statement if you plan to change the data:
CREATE TABLE exercise_4_2 AS SELECT payment_id , customer_id , amount , payment_date FROM payment WHERE payment_id BETWEEN 101 AND 120; |
Alternatively, you can create an exercise_4_2 view with the following SQL statement if you plan to only query the data:
CREATE VIEW exercise_4_2 AS SELECT payment_id , customer_id , amount , payment_date FROM payment WHERE payment_id BETWEEN 101 AND 120; |
After creating the new exercise_4_2 table or view from the payment table it will hold a subset of data. You can query all the rows from the new exercise_4_2 table or view with this statement:
SELECT * FROM exercise_4_2; |
It returns the following data set:
+------------+-------------+--------+---------------------+ | payment_id | customer_id | amount | payment_date | +------------+-------------+--------+---------------------+ | 101 | 4 | 8.99 | 2005-08-18 05:14:44 | | 102 | 4 | 1.99 | 2005-08-19 02:19:13 | | 103 | 4 | 2.99 | 2005-08-20 09:32:04 | | 104 | 4 | 6.99 | 2005-08-20 12:55:40 | | 105 | 4 | 4.99 | 2005-08-21 04:53:37 | | 106 | 4 | 2.99 | 2005-08-22 13:58:23 | | 107 | 4 | 1.99 | 2005-08-23 07:43:00 | | 108 | 5 | 0.99 | 2005-05-29 07:25:16 | | 109 | 5 | 6.99 | 2005-05-31 11:15:43 | | 110 | 5 | 1.99 | 2005-05-31 19:46:38 | | 111 | 5 | 3.99 | 2005-06-15 22:03:14 | | 112 | 5 | 2.99 | 2005-06-16 08:01:02 | | 113 | 5 | 4.99 | 2005-06-17 15:56:53 | | 114 | 5 | 2.99 | 2005-06-19 04:20:13 | | 115 | 5 | 4.99 | 2005-06-20 18:38:22 | | 116 | 5 | 4.99 | 2005-07-06 09:11:58 | | 117 | 5 | 2.99 | 2005-07-08 20:04:43 | | 118 | 5 | 4.99 | 2005-07-09 01:57:57 | | 119 | 5 | 5.99 | 2005-07-09 07:13:52 | | 120 | 5 | 1.99 | 2005-07-09 08:51:42 | +------------+-------------+--------+---------------------+ 20 rows in set (0.26 sec) |
With the exercise_4_2 table, you can test the exercises 4-1 and 4-2. Here are the two problems:
- The first exercise checks for rows where the customer_id is not equal to 5 and whether the amount is greater than 8 or payment_date is equal to ‘2005-08-23’. You can structure that question as the following query:
mysql> SELECT * -> FROM exercise_4_2 -> WHERE customer_id <> 5 -> AND (amount > 8 OR DATE(payment_date) = '2005-08-23');
It would return the following two rows from the exercise_4_2 table:
+------------+-------------+--------+---------------------+ | payment_id | customer_id | amount | payment_date | +------------+-------------+--------+---------------------+ | 101 | 4 | 8.99 | 2005-08-18 05:14:44 | | 107 | 4 | 1.99 | 2005-08-23 07:43:00 | +------------+-------------+--------+---------------------+ 2 rows in set (0.14 sec)
- The second exercise checks for rows where the customer_id is equal to 5 and whether the amount is not greater than 6 or payment_date is not equal to ‘2005-06-19’. You can structure that question as the following query:
mysql> SELECT * -> FROM exercise_4_2 -> WHERE customer_id = 5 -> AND NOT (amount > 6 OR DATE(payment_date) = '2005-06-19');
It would return the following eleven rows from the exercise_4_2 table:
+------------+-------------+--------+---------------------+ | payment_id | customer_id | amount | payment_date | +------------+-------------+--------+---------------------+ | 108 | 5 | 0.99 | 2005-05-29 07:25:16 | | 110 | 5 | 1.99 | 2005-05-31 19:46:38 | | 111 | 5 | 3.99 | 2005-06-15 22:03:14 | | 112 | 5 | 2.99 | 2005-06-16 08:01:02 | | 113 | 5 | 4.99 | 2005-06-17 15:56:53 | | 115 | 5 | 4.99 | 2005-06-20 18:38:22 | | 116 | 5 | 4.99 | 2005-07-06 09:11:58 | | 117 | 5 | 2.99 | 2005-07-08 20:04:43 | | 118 | 5 | 4.99 | 2005-07-09 01:57:57 | | 119 | 5 | 5.99 | 2005-07-09 07:13:52 | | 120 | 5 | 1.99 | 2005-07-09 08:51:42 | +------------+-------------+--------+---------------------+ 11 rows in set (0.00 sec)
- The third exercise checks for payment_id and amount values where the amount is either 1.98, 7.98, or 9.98. You can structure that question as the following query:
mysql> SELECT payment_id -> , amount -> FROM payment -> WHERE amount IN (1.98,7.98,9.98);
It would return the following seven rows from the payment table:
+------------+--------+ | payment_id | amount | +------------+--------+ | 1482 | 7.98 | | 1670 | 9.98 | | 2901 | 1.98 | | 4234 | 7.98 | | 4449 | 7.98 | | 7243 | 7.98 | | 9585 | 7.98 | +------------+--------+ 7 rows in set (0.00 sec)
- The fourth exercise checks for the first_name and last_name of customers where the last_name contains an ‘A’ in the second position and a ‘W’ after the ‘A’ character. You can structure that question as the following query:
mysql> SELECT first_name -> , last_name -> FROM customer -> WHERE last_name LIKE '_A%W%';
The trick to the
WHERE
clause is that the ‘%’ looks for zero to many characters in between two strings.It would return the following nine rows from the customer table:
+------------+------------+ | first_name | last_name | +------------+------------+ | JILL | HAWKINS | | ERICA | MATTHEWS | | LAURIE | LAWRENCE | | JEANNE | LAWSON | | KAY | CALDWELL | | JOHN | FARNSWORTH | | SAMUEL | MARLOW | | LAWRENCE | LAWTON | | LEE | HAWKS | +------------+------------+ 9 rows in set (0.10 sec)
As always, I hope this helps those looking for a solution.
MySQL PHP Transaction
My students liked the MySQL Transaction post but wanted one that showed how an external web application would interact with MySQL in the scope of a transaction. So, I put a little PHP function together that write across two related tables in the context of a transaction. It uses mysqli (MySQL Improved Extension) to connect PHP to the MySQL database.
The function is barebones and uses the oldest approach of hidden inputs to maintain context between rendered forms using an HTML POST method. The hidden inputs are preceded with “h_” and snake case is used for variable names.
The function only writes to two tables. It writes to the member table and when that completes successfully to the contact table. The function:
- Submits credentials from a file and raises an error when they don’t work.
- Initializes a SQL statement.
- Disables auto commit.
- Starts a transaction.
- Defines a first SQL statement with placeholders.
- Binds local variables to the first SQL statement’s placeholders.
- Rolls back the transaction when the first statement fails and continues to the next SQL statement when first statement succeeds.
- Defines a second SQL statement with placeholders.
- Binds local variables to the second SQL statement’s placeholders.
- Rolls back the transaction when the second statement fails and commits the work when the second statement succeeds.
- Closes a SQL statement.
The code for the PHP function is:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 | /* || Function Name: update_membership || ---------------------------------------------------------------------- || No return, treated as a procedure, or method returning a void. || ---------------------------------------------------------------------- */ function update_membership( $h_account_number , $h_member_type , $h_credit_card_number , $h_credit_card_type , $account_number , $member_type , $credit_card_number , $credit_card_type , $h_first_name , $h_middle_name , $h_last_name , $h_contact_type , $first_name , $middle_name , $last_name , $contact_type) { // Include the credentials file if omitted. include_once("MySQLCredentials.inc"); // Assign credentials to connection. $mysqli = new mysqli(HOSTNAME, USERNAME, PASSWORD, DATABASE); // Check for connection error and print message. if ($mysqli->connect_errno) { print $mysqli->connect_error."<br />"; print "Connection not established ...<br />"; } else { // Initial statement. $stmt = $mysqli->stmt_init(); // Disable auto commit when you want two plus statements run. $mysqli->autocommit(FALSE); // Set the transaction guarantee. $mysqli->begin_transaction(MYSQLI_TRANS_START_READ_WRITE); // Declare a static query. $sql = "UPDATE member\n" . "SET member_type = ?\n" . ", credit_card_number = ?\n" . ", credit_card_type = ?\n" . "WHERE account_number = ?\n" . "AND member_type = ?\n" . "AND credit_card_number = ?\n" . "AND credit_card_type = ?\n"; // Prepare statement. if ($stmt->prepare($sql)) { $stmt->bind_param( "sssssss" , $member_type , $credit_card_number , $credit_card_type , $account_number , $h_member_type , $h_credit_card_number , $h_credit_card_type); } // Attempt query and exit with failure before processing. if (!$stmt->execute()) { // Rollback or undo the transaction. $mysqli->rollback(); // Print failure to resolve query message. print $mysqli->error."<br />\n"; print "Failed to resolve query ...<br />\n"; } // Declare a static query. $sql = "UPDATE contact\n" . "SET first_name = ?\n" . ", middle_name = ?\n" . ", last_name = ?\n" . ", contact_type = ?\n" . "WHERE first_name = ?\n" . "AND middle_name = ?\n" . "AND last_name = ?\n" . "AND contact_type = ?\n"; // Prepare statement. if ($stmt->prepare($sql)) { $stmt->bind_param( "ssssssss" , $first_name , $middle_name , $last_name , $contact_type , $h_first_name , $h_middle_name , $h_last_name , $h_contact_type); } // Attempt query and exit with failure before processing. if (!$stmt->execute()) { // Rollback or undo the transaction. $mysqli->rollback(); // Print failure to resolve query message. print $mysqli->error."<br />"; print "Failed to resolve query ...<br />"; } else { /* Manually commiting writes when you have disabled the || default auto commit setting, explained above. || ------------------------------------------------------------ || You would add the following command to commit the || transaction. || ------------------------------ || $mysqli->commit(); || ------------------------------------------------------------ */ $mysqli->commit(); // Close the transaction. $mysqli->close(); } } } |
Line 41 disables auto commit and line 44 starts the transaction. Each statement is managed with the subsequent statement nested inside a block of code that is only reachable when the prior statement succeeds. While this only uses the member and contact table, it could use any number of tables. The natural alternative is building an updatable view.
As always, I hope this helps anybody looking for a code complete example.
SQL Handling Nulls
Interesting questions always come via my students. For example, “Why does the selective aggregation sample return null values as totals from the SUM()
function in MySQL?”
First, here’s the code to build the sample table for the problem:
DROP TABLE IF EXISTS transaction; CREATE TABLE transaction ( transaction_id int unsigned primary key auto_increment , transaction_date date , transaction_amount double ); INSERT INTO transaction ( transaction_date, transaction_amount ) VALUES ('2021-01-10', 56) ,('2021-02-14',23.02) ,('2021-03-31',31.06) ,('2021-01-01',.25) ,('2020-01-02', 52) ,('2020-02-08',22.02) ,('2020-03-26',32.06) ,('2020-01-12',.75);; |
Now, here’s the selective aggregation query:
SELECT EXTRACT(YEAR FROM transaction_date) AS "Year" , SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 1 THEN transaction_amount END) AS "Jan" , SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 2 THEN transaction_amount END) AS "Feb" , SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 3 THEN transaction_amount END) AS "Mar" , SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) IN (1,2,3) THEN transaction_amount END) AS "1FQ" FROM transaction WHERE transaction_date BETWEEN '2020-01-15' AND '2021-03-15' GROUP BY EXTRACT(YEAR FROM transaction_date) ORDER BY 1; |
It produces the following correct results (at least in response to the query above):
+------+-------+-------+-------+-------+ | Year | Jan | Feb | Mar | 1FQ | +------+-------+-------+-------+-------+ | 2020 | NULL | 22.02 | 32.06 | 54.08 | | 2021 | 56.25 | 23.02 | NULL | 79.27 | +------+-------+-------+-------+-------+ 2 rows in set (0.02 sec) |
Why do you get null values for January 2020 and March 2021? That’s because the query returns null values when the conditions in the SELECT
-list aren’t met for a row return. This happens:
- When a row is returned for the month of February or March a null is returned in the January column.
- When a row is returned for the month of January or March a null is returned in the February column.
- When a row is returned for the month of January or February a null is returned in the March column.
That means there needs to be an ELSE
clause in each of the CASE
statements that sets the return value to zero. For example, the following query includes the ELSE
clause and some nice formatting tricks:
SELECT EXTRACT(YEAR FROM transaction_date) AS "Year" , CONCAT('$',LPAD(FORMAT(SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 1 THEN transaction_amount ELSE 0 END),2),8,' ')) AS "Jan" , LPAD(FORMAT(SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 2 THEN transaction_amount ELSE 0 END),2),8,' ') AS "Feb" , LPAD(FORMAT(SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) = 3 THEN transaction_amount ELSE 0 END),2),8,' ') AS "Mar" , LPAD(FORMAT(SUM( CASE WHEN EXTRACT(MONTH FROM transaction_date) IN (1,2,3) THEN transaction_amount ELSE 0 END),2),8,' ') AS "1FQ" FROM transaction WHERE transaction_date BETWEEN '2020-01-15' AND '2021-03-15' GROUP BY EXTRACT(YEAR FROM transaction_date) ORDER BY 1; |
It returns:
+------+-----------+----------+----------+----------+ | Year | Jan | Feb | Mar | 1FQ | +------+-----------+----------+----------+----------+ | 2020 | $ 0.00 | 22.02 | 32.06 | 54.08 | | 2021 | $ 56.25 | 23.02 | 0.00 | 79.27 | +------+-----------+----------+----------+----------+ 2 rows in set (0.01 sec) |
As always, I hope this helps answer a question that somebody is trying to sort out.
MySQL Outer Joins
The students needed yet another example of LEFT JOIN
, RIGHT JOIN
, and FULL JOIN
syntax (by combining a left and right join with the UNION set operator). To that end, I put this set of examples together.
The example also shows how to order the result set from a derived table with the UNION
operator. It uses the WITH
clause to build a Common Table Expression (CTE), which allows the query to order the UNION
set operator’s product based on the left and right join queries. It uses a CASE
statement to order the result sets. The left_table
is the parent table and the right_table
is the child table in the relationship, which means the right_table
holds a left_id
foreign key column that lets you connect matching rows in the left_table
.
You build the little model with the following script:
-- ----------------------------------------------------------------- -- Drop the demonstration tables. -- ----------------------------------------------------------------- DROP TABLE IF EXISTS left_table, right_table; -- ----------------------------------------------------------------- -- Create left_table. -- ----------------------------------------------------------------- CREATE TABLE left_table ( left_id int unsigned primary key auto_increment , leftstring varchar(10)); -- ----------------------------------------------------------------- -- Create left_table. -- ----------------------------------------------------------------- CREATE TABLE right_table ( right_id int unsigned primary key auto_increment , left_id int unsigned , rightstring varchar(10)); -- ----------------------------------------------------------------- -- Insert five rows to the left table, which holds a -- left_id primary key column. -- ----------------------------------------------------------------- INSERT INTO left_table (leftstring) values ('One'); INSERT INTO left_table (leftstring) values ('Two'); INSERT INTO left_table (leftstring) values ('Three'); INSERT INTO left_table (leftstring) values ('Four'); INSERT INTO left_table (leftstring) values ('Five'); -- ----------------------------------------------------------------- -- Delete row four to create a gap. -- ----------------------------------------------------------------- DELETE FROM left_table where left_id = 4; -- ----------------------------------------------------------------- -- Insert four rows, skipping a foreign key value for the -- left_id primary key value of 2. -- ----------------------------------------------------------------- INSERT INTO right_table (rightstring,left_id) values ('One',1); INSERT INTO right_table (rightstring,left_id) values ('Three',3); INSERT INTO right_table (rightstring,left_id) values ('Four',4); INSERT INTO right_table (rightstring,left_id) values ('Five',5); |
Here are the join statements:
INNER JOIN
The INNER JOIN only returns those rows that match between a primary and foreign key column or set of columns.
SELECT l.left_id , l.leftstring , r.left_id , r.right_id , r.rightstring FROM left_table l INNER JOIN right_table r ON l.left_id = r.left_id; |
It produces the following result set:
+---------+------------+---------+----------+-------------+ | left_id | leftstring | left_id | right_id | rightstring | +---------+------------+---------+----------+-------------+ | 1 | One | 1 | 1 | One | | 3 | Three | 3 | 2 | Three | | 5 | Five | 5 | 4 | Five | +---------+------------+---------+----------+-------------+ 3 rows in set (0.00 sec) |
LEFT OUTER JOIN
The LEFT OUTER JOIN
only returns those rows that match between a primary and foreign key column or set of columns and any rows in the table on the lefthand side of the join that fail to match with any row on the righthand side of the join. The non-matching rows are also known as the right complement of the join.
1 2 3 4 5 6 7 | SELECT l.left_id , l.leftstring , r.left_id , r.right_id , r.rightstring FROM left_table l LEFT JOIN right_table r ON l.left_id = r.left_id; |
It produces the following result set:
+---------+------------+---------+----------+-------------+ | left_id | leftstring | left_id | right_id | rightstring | +---------+------------+---------+----------+-------------+ | 1 | One | 1 | 1 | One | | 2 | Two | NULL | NULL | NULL | | 3 | Three | 3 | 2 | Three | | 5 | Five | 5 | 4 | Five | +---------+------------+---------+----------+-------------+ 4 rows in set (0.00 sec) |
Add the following line 8 to the query and you get only those rows in the lefthand table that have no child-related rows in the righthand table. These rows are sometimes called childless parent rows. More or less, the use case for this type of query is to find order headers without order lines.
6 7 8 | FROM left_table l LEFT JOIN right_table r ON l.left_id = r.left_id WHERE r.left_id IS NULL; |
It produces the following result set:
+---------+------------+---------+----------+-------------+ | left_id | leftstring | left_id | right_id | rightstring | +---------+------------+---------+----------+-------------+ | 2 | Two | NULL | NULL | NULL | +---------+------------+---------+----------+-------------+ 1 row in set (0.00 sec) |
RIGHT OUTER JOIN
1 2 3 4 5 6 7 | SELECT l.left_id , l.leftstring , r.left_id , r.right_id , r.rightstring FROM left_table l RIGHT JOIN right_table r ON l.left_id = r.left_id; |
It produces the following result set:
+---------+------------+---------+----------+-------------+ | left_id | leftstring | left_id | right_id | rightstring | +---------+------------+---------+----------+-------------+ | 1 | One | 1 | 1 | One | | 3 | Three | 3 | 2 | Three | | NULL | NULL | 4 | 3 | Four | | 5 | Five | 5 | 4 | Five | +---------+------------+---------+----------+-------------+ 4 rows in set (0.00 sec) |
Add the following line 8 to the query and you get only those rows in the righthand table that have no parent-related rows in the lefthand table. These rows are sometimes called orphans because they have no parent row. More or less, the use case for this type of query is to find latent order lines after deleting the order header.
6 7 8 | FROM left_table l LEFT JOIN right_table r ON l.left_id = r.left_id WHERE l.left_id IS NULL; |
It produces the following result set:
+---------+------------+---------+----------+-------------+ | left_id | leftstring | left_id | right_id | rightstring | +---------+------------+---------+----------+-------------+ | NULL | NULL | 4 | 3 | Four | +---------+------------+---------+----------+-------------+ 1 row in set (0.00 sec) |
FULL OUTER JOIN
The full outer join doesn’t exist in MySQL, so you combine a LEFT OUTER JOIN
and RIGHT OUTER JOIN
with the UNION
operator. The UNION
operator eliminates the duplicate row from the intersection of the joins.
Here’s the full query:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | WITH cte AS (SELECT l.left_id AS primary_left_id , l.leftstring , r.left_id AS foreign_left_id , r.right_id , r.rightstring FROM left_table l LEFT JOIN right_table r ON l.left_id = r.left_id UNION SELECT l.left_id AS primary_left_id , l.leftstring , r.left_id AS foreign_left_id , r.right_id , r.rightstring FROM left_table l RIGHT JOIN right_table r ON l.left_id = r.left_id) SELECT * FROM cte ORDER BY CASE WHEN 'One' IN (leftstring, rightstring) THEN 1 WHEN 'Two' IN (leftstring, rightstring) THEN 2 WHEN 'Three' IN (leftstring, rightstring) THEN 3 WHEN 'Four' IN (leftstring, rightstring) THEN 4 WHEN 'Five' IN (leftstring, rightstring) THEN 5 END; |
It produces the following result set:
+-----------------+------------+-----------------+----------+-------------+ | primary_left_id | leftstring | foreign_left_id | right_id | rightstring | +-----------------+------------+-----------------+----------+-------------+ | 1 | One | 1 | 1 | One | | 2 | Two | NULL | NULL | NULL | | 3 | Three | 3 | 2 | Three | | NULL | NULL | 4 | 3 | Four | | 5 | Five | 5 | 4 | Five | +-----------------+------------+-----------------+----------+-------------+ 5 rows in set (0.00 sec) |
Add the following lines 18 and 19 to the query and you get only those rows that are childless parent rows or orphaned child rows. More or less, the use case for this type of query is to find both order headers without order lines and order lines abandoned by deleted order headers.
17 18 19 | SELECT * FROM cte WHERE primary_left_id IS NULL OR foreign_left_id IS NULL |
It produces the following result set:
+-----------------+------------+-----------------+----------+-------------+ | primary_left_id | leftstring | foreign_left_id | right_id | rightstring | +-----------------+------------+-----------------+----------+-------------+ | 2 | Two | NULL | NULL | NULL | | NULL | NULL | 4 | 3 | Four | +-----------------+------------+-----------------+----------+-------------+ 2 rows in set (0.00 sec) |
The ORDER BY
clause used is a variation on the more common choice of:
WHEN leftstring = 'One' OR rightstring = 'One' THEN 1 |
The position of two string literals in any statement is a bad idea. Inverting the literal on the right and using a IN
operator gives you a better and clearer WHEN
statement:
WHEN 'One' IN (leftstring, rightstring) THEN 1 |
As always, I hope this helps those looking for syntax examples.
MySQL INSERT-SET
I found myself explaining the nuances of INSERT
statements and whether you should use named or positional notation. While the class was on Zoom, I could imagine the blank stares in the silence of my headphones. Then, I had to remind them about mandatory (NOT NULL
constrained) and optional (nullable) columns in tables and how an INSERT
statement requires an explicit NULL
value for optional columns when the INSERT
statement isn’t inserting a value into that column.
Then, I asked if somebody could qualify the different types of INSERT
statements; and what would happen if a table with a first_name
and last_name
column order evolves when a new DBA decides to restructure the table and uses a last_name
and first_name
column order in the new table structure. Only a couple of the students recalled using a column-list between the table name and VALUES
clause but none could remember how to write an INSERT-SET
statement.
Below is a quick example of inserting data with column-lists and the SET
clause. It builds an actor
table with an actor_id
column as a surrogate key and primary key column and a unique natural key composed of the first and last name columns (not a real world solution for uniqueness).
CREATE TABLE actor ( actor_id int unsigned primary key auto_increment , first_name varchar(30) not null , last_name varchar(30) not null , CONSTRAINT actor_uq UNIQUE (first_name, last_name)); |
Next, let’s insert a couple rows with a column-list approach. The column-list is a comma-delimited list of column values that must contain all mandatory columns and may contain optional columns.
INSERT INTO actor ( first_name , last_name ) VALUES ('Harrison','Ford') ,('Carrie','Fisher') ,('Mark','Hamill') ,('Alec','Guinness'); |
Now, let’s validate the unique constraint on the composite value of first and last name by trying to insert a second Harrison Ford into the actor table.
INSERT INTO actor (first_name, last_name) VALUES ('Harrison','Ford'); |
it fails and raises the following error:
ERROR 1062 (23000): Duplicate entry 'Harrison-Ford' for key 'actor.actor_uq' |
The following uses the INSERT-SET
statement to add Tom Hanks to the actor table:
INSERT INTO actor SET first_name = 'Tom' , last_name = 'Hanks'; |
I believe the INSERT-SET
is the best approach to a name-value model for INSERT
statements. It’s a shame that only MySQL supports it. Query the actor
table with the following:
SELECT * FROM actor ORDER BY actor_id; |
it returns:
+----------+------------+-----------+ | actor_id | first_name | last_name | +----------+------------+-----------+ | 1 | Harrison | Ford | | 2 | Carrie | Fisher | | 3 | Mark | Hamill | | 4 | Alec | Guinness | | 6 | Tom | Hanks | +----------+------------+-----------+ 5 rows in set (0.01 sec) |
There’s now a gap when you query the data because the second attempt at adding Harrison Ford consumed a sequence value from the internally managed list. That list is a property of the table when you create or alter a table to include an autoincrementing column, like actor_id
. Anytime you attempt to insert a row that violates the table constraints, you consume a value from the internally managed sequence. While you can restore it and eliminate the gaps, I strongly recommend against it.
As always, I hope this helps those trying to learn and experiment with syntax.
MySQL Connect Dialog
About a month ago, I published how you can connect to MySQL with a small form. One suggestion, or lets promote it to a request, from that post was: “Nice, but how do you create a reusable library for the MySQL Connection Dialog box?”
That was a good question but I couldn’t get back until now to write a new blog post. This reusable MySQL connection dialog lets you remove MySQL connection data from the command-line history. This post also shows you how to create and test a Powershell Module.
The first step to create a module requires that you set the proper %PSModulePath%
environment variable. If you fail to do that, you can put it into a default PowerShell module location but that’s not too effective for testing. You launch the System Properties dialog and click the Environment Variables button:
Then, you edit the PSModulePath environment variable in the bottom list of environment variables and add a new path to the PSModulePath. My development path in this example is:
C:\Data\cit225\mysql\ps\mod |
I named the file the same as the function Get-Credentials.psm1 consistent with the Microsoft instructions for creating a PowerShell module and their instructions for Pascal case name with an approved verb and singular noun.
Below is the code for the Get-Credentials.psm1
file:
function Get-Credentials { # Add libraries for form components. Add-Type -AssemblyName System.Windows.Forms Add-Type -AssemblyName System.Drawing # Define a user credential form. $form = New-Object System.Windows.Forms.Form $form.Text = 'User Credential Form' $form.Size = New-Object System.Drawing.Size(300,240) $form.StartPosition = 'CenterScreen' # Define a button and assign it and its controls to a form. $loginButton = New-Object System.Windows.Forms.Button $loginButton.Location = New-Object System.Drawing.Point(60,160) $loginButton.Size = New-Object System.Drawing.Size(75,23) $loginButton.Text = 'Login' $loginButton.DialogResult = [System.Windows.Forms.DialogResult]::OK $form.AcceptButton = $loginButton $form.Controls.Add($loginButton) # Define a button and assign it and its controls to a form. $cancelButton = New-Object System.Windows.Forms.Button $cancelButton.Location = New-Object System.Drawing.Point(155,160) $cancelButton.Size = New-Object System.Drawing.Size(75,23) $cancelButton.Text = 'Cancel' $cancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel $form.CancelButton = $cancelButton $form.Controls.Add($cancelButton) # Define a label and assign it and its controls to a form. $userLabel = New-Object System.Windows.Forms.Label $userLabel.Location = New-Object System.Drawing.Point(30,15) $userLabel.Size = New-Object System.Drawing.Size(100,20) $userLabel.Text = 'Enter User Name:' $form.Controls.Add($userLabel) # Define a TextBox and assign it and its controls to a form. $userTextBox = New-Object System.Windows.Forms.TextBox $userTextBox.Location = New-Object System.Drawing.Point(140,15) $userTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($userTextBox) # Define a label and assign it and its controls to a form. $pwdLabel = New-Object System.Windows.Forms.Label $pwdLabel.Location = New-Object System.Drawing.Point(30,40) $pwdLabel.Size = New-Object System.Drawing.Size(100,20) $pwdLabel.Text = 'Enter Password:' $form.Controls.Add($pwdLabel) # Define a TextBox and assign it and its controls to a form. $pwdTextBox = New-Object System.Windows.Forms.TextBox $pwdTextBox.Location = New-Object System.Drawing.Point(140,40) $pwdTextBox.Size = New-Object System.Drawing.Size(100,20) $pwdTextBox.PasswordChar = "*" $form.Controls.Add($pwdTextBox) # Define a label and assign it and its controls to a form. $hostLabel = New-Object System.Windows.Forms.Label $hostLabel.Location = New-Object System.Drawing.Point(30,65) $hostLabel.Size = New-Object System.Drawing.Size(100,20) $hostLabel.Text = 'Enter Hostname:' $form.Controls.Add($hostLabel) # Define a TextBox and assign it and its controls to a form. $hostTextBox = New-Object System.Windows.Forms.TextBox $hostTextBox.Location = New-Object System.Drawing.Point(140,65) $hostTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($hostTextBox) # Define a label and assign it and its controls to a form. $portLabel = New-Object System.Windows.Forms.Label $portLabel.Location = New-Object System.Drawing.Point(30,90) $portLabel.Size = New-Object System.Drawing.Size(100,20) $portLabel.Text = 'Enter Port #:' $form.Controls.Add($portLabel) # Define a TextBox and assign it and its controls to a form. $portTextBox = New-Object System.Windows.Forms.TextBox $portTextBox.Location = New-Object System.Drawing.Point(140,90) $portTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($portTextBox) # Define a label and assign it and its controls to a form. $dbLabel = New-Object System.Windows.Forms.Label $dbLabel.Location = New-Object System.Drawing.Point(30,115) $dbLabel.Size = New-Object System.Drawing.Size(100,20) $dbLabel.Text = 'Enter DB Name:' $form.Controls.Add($dbLabel) # Define a TextBox and assign it and its controls to a form. $dbTextBox = New-Object System.Windows.Forms.TextBox $dbTextBox.Location = New-Object System.Drawing.Point(140,115) $dbTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($dbTextBox) $form.Topmost = $true $form.Add_Shown({$userTextBox.Select()}) $result = $form.ShowDialog() if ($result -eq [System.Windows.Forms.DialogResult]::OK) { # Assign inputs to connection variables. $uid = $userTextBox.Text $pwd = $pwdTextBox.Text $server = $hostTextBox.Text $port= $portTextBox.Text $dbName = $dbTextBox.Text # Declare connection string. $credentials = 'server=' + $server + ';port=' + $port + ';uid=' + $uid + ';pwd=' + $pwd + ';database=' + $dbName } else { $credentials = $null } return $credentials } |
You must create a Get-Connection
directory in your C:\Data\cit225\mysql\ps\mod
directory that you added to the PSModulePath. Then, you must put your module code in the Get-Connection
subdirectory as the Get-Connection.psm1
module file.
The test.ps1
script imports the Get-Credentials.psm1
PowerShell module, launches the MySQL Connection Dialog form and returns the connection string. The test.ps1
code is:
# Import your custom module. Import-Module Get-Credentials # Test the Get-Credentials function. if (($credentials = Get-Credentials) -ne $undefinedVariable) { Write-Host($credentials) } |
You can test it from the local any directory with the following command-line:
powershell .\test.ps1 |
It should print something like this to the console:
server=localhost;port=3306;uid=student;pwd=student;database=studentdb |
If you got this far, that’s great! You’re ready to test a connection to the MySQL database. Before you do that, you should create the same avenger
table I used in the initial post and insert the same or some additional data. Connect to the any of your test databases and rung the following code to create the avenger table and nine rows of data.
-- Create the avenger table. CREATE TABLE db_connect ( db_connect_id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT , version VARCHAR(10) , user VARCHAR(24) , db_name VARCHAR(10)); -- Seed the avenger table with data. INSERT INTO avenger ( first_name, last_name, avenger ) VALUES ('Anthony', 'Stark', 'Iron Man') ,('Thor', 'Odinson', 'God of Thunder') ,('Steven', 'Rogers', 'Captain America') ,('Bruce', 'Banner', 'Hulk') ,('Clinton', 'Barton', 'Hawkeye') ,('Natasha', 'Romanoff', 'Black Widow') ,('Peter', 'Parker', 'Spiderman') ,('Steven', 'Strange', 'Dr. Strange') ,('Scott', 'Lange', 'Ant-man'); |
Now, let’s promote our use-case test.ps1
script to a testQuery.ps1
script, like:
# Import your custom module. Import-Module Get-Credentials # Test the Get-Credentials function. if (($credentials = Get-Credentials) -ne $undefinedVariable) { # Connect to the libaray MySQL.Data.dll Add-Type -Path 'C:\Program Files (x86)\MySQL\Connector NET 8.0\Assemblies\v4.5.2\MySql.Data.dll' # Create a MySQL Database connection variable that qualifies: # [Driver]@ConnectionString # ============================================================ # You can assign the connection string before using it or # while using it, which is what we do below by assigning # literal values for the following names: # - server=<ip_address> or 127.0.0.1 for localhost # - uid=<user_name> # - pwd=<password> # - port=<port#> or 3306 for default port # - database=<database_name> # ============================================================ $Connection = [MySql.Data.MySqlClient.MySqlConnection]@{ConnectionString=$credentials} $Connection.Open() # Define a MySQL Command Object for a non-query. $sqlCommand = New-Object MySql.Data.MySqlClient.MySqlCommand $sqlDataAdapter = New-Object MySql.Data.MySqlClient.MySqlDataAdapter $sqlDataSet = New-Object System.Data.DataSet # Assign the connection and command text to the MySQL command object. $sqlCommand.Connection = $Connection $sqlCommand.CommandText = 'SELECT CONCAT(first_name," ",last_name) AS full_name ' + ', avenger ' + 'FROM avenger' # Assign the connection and command text to the query method of # the data adapter object. $sqlDataAdapter.SelectCommand=$sqlCommand # Assign the tuples of data to a data set and return the number of rows fetched. $rowsFetched=$sqlDataAdapter.Fill($sqlDataSet, "data") # Print to console the data returned from the query. foreach($row in $sqlDataSet.tables[0]) { write-host "Avenger:" $row.avenger "is" $row.full_name } # Close the MySQL connection. $Connection.Close() } |
It should give you the MySQL Connection Dialog and with the correct credentials print the following to your console:
Avenger: Iron Man is Anthony Stark Avenger: God of Thunder is Thor Odinson Avenger: Captain America is Steven Rogers Avenger: Hulk is Bruce Banner Avenger: Hawkeye is Clinton Barton Avenger: Black Widow is Natasha Romanoff Avenger: Spiderman is Peter Parker Avenger: Dr. Strange is Steven Strange Avenger: Ant-man is Scott Lange |
As always, I hope this helps those looking to exploit technology.
MySQL Transaction Unit
Many of my students wanted to know how to write a simple PSM (Persistent Stored Module) for MySQL that saved the writes to all table as a group. So, to that end here’s simple example.
- Create four sample tables in a re-runnable script file:
/* Drop and create four tables. */ DROP TABLE IF EXISTS one, two, three, four; CREATE TABLE one ( id int primary key auto_increment, msg varchar(10)); CREATE TABLE two ( id int primary key auto_increment, msg varchar(10)); CREATE TABLE three ( id int primary key auto_increment, msg varchar(10)); CREATE TABLE four ( id int primary key auto_increment, msg varchar(10));
- Create a locking PSM across the four tables:
/* Conditionally drop procedure. */ DROP PROCEDURE IF EXISTS locking; /* Set delimiter to $$ to allow ; inside the procedure. */ DELIMITER $$ /* Create a transaction procedure. */ CREATE PROCEDURE locking(IN pv_one varchar(10) ,IN pv_two varchar(10) ,IN pv_three varchar(10) ,IN pv_four varchar(10)) BEGIN /* Declare an EXIT Handler when a string is too long for a column. Undo all prior writes with a ROLLBACK statement. */ DECLARE EXIT HANDLER FOR 1406 BEGIN ROLLBACK; END; /* Start transaction scope. */ START TRANSACTION; /* A series of INSERT statement. */ INSERT INTO one (msg) VALUES (pv_one); INSERT INTO two (msg) VALUES (pv_two); INSERT INTO three (msg) VALUES (pv_three); INSERT INTO four (msg) VALUES (pv_four); /* Commit transaction set. */ COMMIT; END; $$ /* Reset delimiter to ; for SQL statements. */ DELIMITER ;
- Test program for inserting the data:
/* Call locking procedure. */ CALL locking('Donald','Goofy','Mickey','Pluto'); CALL locking('Squirrel','Chipmunk','Monkey business','Raccoon'); CALL locking('Curly','Larry','Moe','Shemp');
- Verify the test results:
/* Select from tables, which should be empty. */ SELECT * FROM one; SELECT * FROM two; SELECT * FROM three; SELECT * FROM four;
As always, I hope this code complete example helps those trying to figure things out.
MySQL+Credentials
The first tutorial supplementing the MySQL Connector/NET Developer Guide showed you how to connect and run static INSERT
statement. It was a barebones PowerShell script with the MySQL Connector. This post shows you how to run a PowerShell script that uses a dynamic form to gather the MySQL credentials and then run a static query. Below is the MySQL Credentials form.
You enter the correct user name, password, hostname (or IP address), port, and database, like this:
Here’s the complete code for this staticQuery.ps1
PowerShell script:
# Add libraries for form components. Add-Type -AssemblyName System.Windows.Forms Add-Type -AssemblyName System.Drawing # Define a user credential form. $form = New-Object System.Windows.Forms.Form $form.Text = 'User Credential Form' $form.Size = New-Object System.Drawing.Size(300,240) $form.StartPosition = 'CenterScreen' # Define a button and assign it and its controls to a form. $loginButton = New-Object System.Windows.Forms.Button $loginButton.Location = New-Object System.Drawing.Point(60,160) $loginButton.Size = New-Object System.Drawing.Size(75,23) $loginButton.Text = 'Login' $loginButton.DialogResult = [System.Windows.Forms.DialogResult]::OK $form.AcceptButton = $loginButton $form.Controls.Add($loginButton) # Define a button and assign it and its controls to a form. $cancelButton = New-Object System.Windows.Forms.Button $cancelButton.Location = New-Object System.Drawing.Point(155,160) $cancelButton.Size = New-Object System.Drawing.Size(75,23) $cancelButton.Text = 'Cancel' $cancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel $form.CancelButton = $cancelButton $form.Controls.Add($cancelButton) # Define a label and assign it and its controls to a form. $userLabel = New-Object System.Windows.Forms.Label $userLabel.Location = New-Object System.Drawing.Point(30,15) $userLabel.Size = New-Object System.Drawing.Size(100,20) $userLabel.Text = 'Enter User Name:' $form.Controls.Add($userLabel) # Define a TextBox and assign it and its controls to a form. $userTextBox = New-Object System.Windows.Forms.TextBox $userTextBox.Location = New-Object System.Drawing.Point(140,15) $userTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($userTextBox) # Define a label and assign it and its controls to a form. $pwdLabel = New-Object System.Windows.Forms.Label $pwdLabel.Location = New-Object System.Drawing.Point(30,40) $pwdLabel.Size = New-Object System.Drawing.Size(100,20) $pwdLabel.Text = 'Enter Password:' $form.Controls.Add($pwdLabel) # Define a TextBox and assign it and its controls to a form. $pwdTextBox = New-Object System.Windows.Forms.TextBox $pwdTextBox.Location = New-Object System.Drawing.Point(140,40) $pwdTextBox.Size = New-Object System.Drawing.Size(100,20) $pwdTextBox.PasswordChar = "*" $form.Controls.Add($pwdTextBox) # Define a label and assign it and its controls to a form. $hostLabel = New-Object System.Windows.Forms.Label $hostLabel.Location = New-Object System.Drawing.Point(30,65) $hostLabel.Size = New-Object System.Drawing.Size(100,20) $hostLabel.Text = 'Enter Hostname:' $form.Controls.Add($hostLabel) # Define a TextBox and assign it and its controls to a form. $hostTextBox = New-Object System.Windows.Forms.TextBox $hostTextBox.Location = New-Object System.Drawing.Point(140,65) $hostTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($hostTextBox) # Define a label and assign it and its controls to a form. $portLabel = New-Object System.Windows.Forms.Label $portLabel.Location = New-Object System.Drawing.Point(30,90) $portLabel.Size = New-Object System.Drawing.Size(100,20) $portLabel.Text = 'Enter Port #:' $form.Controls.Add($portLabel) # Define a TextBox and assign it and its controls to a form. $portTextBox = New-Object System.Windows.Forms.TextBox $portTextBox.Location = New-Object System.Drawing.Point(140,90) $portTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($portTextBox) # Define a label and assign it and its controls to a form. $dbLabel = New-Object System.Windows.Forms.Label $dbLabel.Location = New-Object System.Drawing.Point(30,115) $dbLabel.Size = New-Object System.Drawing.Size(100,20) $dbLabel.Text = 'Enter DB Name:' $form.Controls.Add($dbLabel) # Define a TextBox and assign it and its controls to a form. $dbTextBox = New-Object System.Windows.Forms.TextBox $dbTextBox.Location = New-Object System.Drawing.Point(140,115) $dbTextBox.Size = New-Object System.Drawing.Size(100,20) $form.Controls.Add($dbTextBox) $form.Topmost = $true $form.Add_Shown({$userTextBox.Select()}) $result = $form.ShowDialog() if ($result -eq [System.Windows.Forms.DialogResult]::OK) { # Assign inputs to connection variables. $uid = $userTextBox.Text $pwd = $pwdTextBox.Text $server = $hostTextBox.Text $port= $portTextBox.Text $dbName = $dbTextBox.Text # Declare connection string. $credentials = 'server=' + $server + ';port=' + $port + ';uid=' + $uid + ';pwd=' + $pwd + ';database=' + $dbName # Connect to the libaray MySQL.Data.dll Add-Type -Path 'C:\Program Files (x86)\MySQL\Connector NET 8.0\Assemblies\v4.5.2\MySql.Data.dll' # Create a MySQL Database connection variable that qualifies: # [Driver]@ConnectionString # ============================================================ # You can assign the connection string before using it or # while using it, which is what we do below by assigning # literal values for the following names: # - server=<ip_address> or 127.0.0.1 for localhost # - port=<port #> # - uid=<user_name> # - pwd=<password> # - database=<database_name> # ============================================================ $Connection = [MySql.Data.MySqlClient.MySqlConnection]@{ConnectionString=$credentials} $Connection.Open() # Define a MySQL Command Object for a non-query. $sqlCommand = New-Object MySql.Data.MySqlClient.MySqlCommand $sqlDataAdapter = New-Object MySql.Data.MySqlClient.MySqlDataAdapter $sqlDataSet = New-Object System.Data.DataSet # Assign the connection and command text to the MySQL command object. $sqlCommand.Connection = $Connection $sqlCommand.CommandText = 'SELECT CONCAT(first_name," ",last_name) AS full_name ' + ', avenger ' + 'FROM avenger' # Assign the connection and command text to the query method of # the data adapter object. $sqlDataAdapter.SelectCommand=$sqlCommand # Assign the tuples of data to a data set and return the number of rows fetched. $rowsFetched=$sqlDataAdapter.Fill($sqlDataSet, "data") # Print to console the data returned from the query. foreach($row in $sqlDataSet.tables[0]) { write-host "Avenger:" $row.avenger "is" $row.full_name } # Close the MySQL connection. $Connection.Close() } |
I created an avenger
table and populated it with six rows of data:
-- Create the avenger table. CREATE TABLE db_connect ( db_connect_id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT , version VARCHAR(10) , user VARCHAR(24) , db_name VARCHAR(10)); -- Seed the avenger table with data. INSERT INTO avenger ( first_name, last_name, avenger ) VALUES ('Anthony', 'Stark', 'Iron Man') ,('Thor', 'Odinson', 'God of Thunder') ,('Steven', 'Rogers', 'Captain America') ,('Bruce', 'Banner', 'Hulk') ,('Clinton', 'Barton', 'Hawkeye') ,('Natasha', 'Romanoff', 'Black Widow'); |
You run the staticQuery.ps1
PowerShell script from the Windows command shell with the following syntax:
powershell .\staticQuery.ps1 |
After running the staticQuery.ps1
PowerShell script, it writes the following to the local console but with minimal effort you can redirect it to a file:
Avenger: Iron Man is Anthony Stark Avenger: God of Thunder is Thor Odinson Avenger: Captain America is Steven Rogers Avenger: Hulk is Bruce Banner Avenger: Hawkeye is Clinton Barton Avenger: Black Widow is Natasha Romanoff |
As always, I hope this helps those looking to use this technology. My guess is the principal uses will be DevOps and Data Engineers.