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Node.js & MySQL

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These are my notes for creating a small Node.js application that queries a MySQL database. The post will show you how to:

  1. Configure your Node.js development directory.
  2. Build a small application to test a MySQL connection.
  3. Build a small application that connects to the MySQL database and queries data.

This blog post assumes you’ve performed a global install of Node.js on a Linux server. If you’re unfamiliar with how to perform a global Node.js installation, I cover how to do it in this earlier blog post.

Before you write the Node.js applicaiton, you need to setup a db developer directory. Then, create a node_modules symbolic link to the /usr/local/lib/node_modules directory in the db directory. You can use the following command from the db directory:

ln -s /usr/local/lib/node_modules `pwd`/node_modules

After creating the node_modules symbolic link, you need to run the following two npm commands:

npm init --y
npm install --save mysql

The first command sets up a generic package.json file, and the second adds the mysql package and supporting packages to the package.json file. These two steps configure the Node.js side of these examples.

They both require that you create the student user with a native password, like so:

CREATE USER 'student'@'localhost' IDENTIFIED WITH 'mysql_native_password' BY 'student';
GRANT ALL PRIVILEGES ON studentdb.* TO 'student'@'localhost';
FLUSH PRIVILEGES;

The following example shows you how to check a connection to the MySQL database:

const mysql = require('mysql') 
const connection = mysql.createConnection({ 
   host: 'localhost', 
   user: 'student', 
   password: 'student', 
   database: 'studentdb' 
}) 
 
connection.connect((err) => { 
 if (err) 
   throw err 
 else 
   console.log('Connected to MySQL Server!\n') 
   console.log('User configured wiht mysql_native_password.\n'); 
   console.log('Press Ctrl-C to terminate ...') 
})

You extend the previous example by adding a query component and returning the query result value to the console’s log (leveraging the w3school’s Node.js and MySQL tutorial example):

const mysql = require('mysql') 
const connection = mysql.createConnection({ 
   host: 'localhost', 
   user: 'student', 
   password: 'student', 
   database: 'studentdb' 
}) 
 
connection.connect((err) => { 
 if (err) 
   throw err 
 else { 
   console.log('Connected to MySQL Server!\n') 
   connection.query('SELECT DISTINCT item_title FROM item', function (err, result) { 
     if (err) 
       throw err 
     else 
       console.log(result) 
       console.log('Press Ctrl-C to terminate ...') 
   }) 
 } 
})

It should display the following:

Connected to MySQL Server! 
 
[ RowDataPacket { item_title: 'The Hunt for Red October' }, 
 RowDataPacket { item_title: 'Star Wars I' }, 
 RowDataPacket { item_title: 'Star Wars II' }, 
 RowDataPacket { item_title: 'Star Wars III' }, 
 RowDataPacket { item_title: 'The Chronicles of Narnia' }, 
 RowDataPacket { item_title: 'RoboCop' }, 
 RowDataPacket { item_title: 'Pirates of the Caribbean' }, 
 RowDataPacket { item_title: 'MarioKart' }, 
 RowDataPacket { item_title: 'Splinter Cell' }, 
 RowDataPacket { item_title: 'Need for Speed' }, 
 RowDataPacket { item_title: 'The DaVinci Code' }, 
 RowDataPacket { item_title: 'Cars' }, 
 RowDataPacket { item_title: 'Beau Geste' }, 
 RowDataPacket { item_title: 'I Remember Mama' }, 
 RowDataPacket { item_title: 'Tora! Tora! Tora!' }, 
 RowDataPacket { item_title: 'A Man for All Seasons' }, 
 RowDataPacket { item_title: 'Hook' }, 
 RowDataPacket { item_title: 'Around the World in 80 Days' }, 
 RowDataPacket { item_title: 'Harry Potter and the Sorcerer\'s Stone' }, 
 RowDataPacket { item_title: 'Camelot' }, 
 RowDataPacket { item_title: 'Casino Royale' }, 
 RowDataPacket { item_title: 'Die Another Day' }, 
 RowDataPacket { item_title: 'Golden Eye' }, 
 RowDataPacket { item_title: 'Tomorrow Never Dies' }, 
 RowDataPacket { item_title: 'The World Is Not Enough' }, 
 RowDataPacket { item_title: 'Brave Heart' }, 
 RowDataPacket { item_title: 'Christmas Carol' }, 
 RowDataPacket { item_title: 'Scrooge' }, 
 RowDataPacket { item_title: 'Clear and Present Danger' }, 
 RowDataPacket { item_title: 'Harry Potter and the Chamber of Secrets' }, 
 RowDataPacket { item_title: 'Harry Potter and the Prisoner of Azkaban' }, 
 RowDataPacket { item_title: 'Harry Potter and the Goblet of Fire' }, 
 RowDataPacket { item_title: 'Harry Potter and the Order of the Phoenix' }, 
 RowDataPacket { item_title: 'Harry Potter and the Half Blood Prince' }, 
 RowDataPacket { item_title: 'Harry Potter and the Deathly Hallows, Part 1' }, 
 RowDataPacket { item_title: 'Harry Potter and the Deathly Hallows, Part 2' }, 
 RowDataPacket { item_title: 'Tron' }, 
 RowDataPacket { item_title: 'The Avengers' }, 
 RowDataPacket { item_title: 'Thor: The Dark World' } ] 
Press Ctrl-C to terminate ...

As always, I hope this helps those looking to learn

Written by maclochlainn

July 21st, 2020 at 11:51 pm

MySQL 8.0.20 JDBC

without comments

In April, when I updated from MySQL 8.0.17 to MySQL 8.0.19, I found that my Java connection example failed. That’s because of a change in the JDBC driver, which I blogged about then. Starting yesterday, I began updating a base Fedora 30 configuration again to MySQL 8.0.20. I wrote a testing program for the Java JDBC file last time, and when I ran it this time it told me that I didn’t have the JDBC driver installed, or in the $CLASSPATH. My Java diagnostic script, MySQLDriver.java, returned the following error message:

Error: Could not find or load main class MySQLDriver

The Java JDBC test program code is in the prior post. It simply loads the user, password, database, host, and port statically for my student image, which you can update for your MySQL deployment.

You can find the MySQL 8.0 Connector/J installation in Chapter 4 of the MySQL Connector/J 8.0 Developer Guide. The link to page where you can download the Connector/J driver is in Chapter 4, but to save time you can click on the following download link. You’ll find Ubuntu, Debian, SUSE Enterprise Linux Server, Red Hat Enterprise Linux/Oracle Linux, Fedora, Platform Independent, and Source Code at that download link.

I downloaded Fedora 30, 31, and 32 because eventually they get deprecated and sometimes I need the deprecated versions. Since Python 2.7 is deprecated, keeping an old Fedora 30 with both Python 2.7 and 3.7 is very attractive as a developer, keeping these Java libraries is also a potential convenience. On the Fedora 30 platform, you should download:

mysql-connector-java-8.0.20-1.fc30.noarch.rpm

You install the RPM package with the following syntax:

rpm -ivh mysql-connector-java-8.0.20-1.fc30.noarch.rpm

It installs a single mysql-connector-java.jar file in the /usr/share/java directory. Then, you need to export the Java Archive file like so in your .bashrc file:

# Set the Java CLASSPATH path.
export CLASSPATH=/usr/share/java/mysql-connector-java.jar:.

Now, my MySQLDriver Java program returned:

Cannot connect to database server:
The server time zone value 'MDT' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

As qualified in the prior post, it required me to add the following line to my /etc/my.cnf configuration file, which synchronizes the database’s timezone with the operating system.

# Synchronize the MySQL clock with the computer system clock.
default-time-zone='+00:00'

You need to restart the MySQL Daemon to apply the change, like:

sudo systemctl restart mysqld.service

Then, running my MySQL Driver connection test program worked like a charm. It returns the following:

Database connection established
MySQLDriver Version [8.0.20]
Database connection terminated

As always, I hope this helps those looking for a quick solution.

Written by maclochlainn

June 26th, 2020 at 2:26 pm

MySQL 8.0.20 Update

without comments

After I updated a Fedora 30 instance, I could no longer connect to the MySQL database. An attempt to connect raised the following error:

Error: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

My guess was correct, the mysqld.service got removed during the update (a synonym for upgrade). So, I ran the following command as a sudoer user:

sudo systemctl enable mysqld.service

It creates the following symbolic link:

Created symlink /etc/systemd/system/multi-user.target.wants/mysqld.service → /usr/lib/systemd/system/mysqld.service.

That would start the MySQL Daemon (mysqld) on the next restart of the OS. However, I didn’t want to restart to have access to the service. I simply started it with the following command:

sudo systemctl start mysqld.service

Then, I could connect to the MySQL database. As always, I hope this helps those looking for a solution.

Written by maclochlainn

June 25th, 2020 at 12:18 pm

MySQL Linux to Windows

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My students want to transfer their course setup MySQL files from the Linux VM that I provide to Microsoft Windows 10. This post explains how because I found a couple small errors in the Google’d posts they would most likely see.

The first step is required because when I didn’t assign a name or domain to the the Fedora VM, which allows it to run as localhost on any student machine. In tandem, I didn’t assign a static IP address but opted for dynamic IP assignment. That means, the first step to securely copy the files requires you to find the assigned IP address. You can do that with the following Linux command:

ifconfig -a | grep 'inet[[:blank:]]' | head -1 | cut -c 14-30

It would return something like:

192.168.147.198

After you have discovered the IP address, you need to download PuTTy from their web site because includes the pscp (PuTTy Secure Copy) utility. I recommend you click on the MSI (Microsoft Installer Package) file, and install it on your Windows machine. As a rule, you should accept the default location, which is C:\Program Files\PuTTy.

While you could alter your system-level %PATH% environment variable after you install the software, I recommend you only include it in the %PATH% within the scope of a Command (cmd) shell. Navigate to your Windows Start and enter cmd in the search field. It should launch the Command Prompt terminal, which is a terminal emulator.

In the terminal editor, type the following case sensitive command to add the PuTTy directory to your path (yes, it’s case sensitive):

SET PATH=%PATH%;%ProgramFiles%\PuTTy

Now, you can securely copy the files and directory structure from Linux to Windows with the following command (where you replace the traditional server name with the dynamically assigned IP address). You should also be in the target directory where you want the files and directories copied:

C:\Data\cit225>pscp -r student@192.168.147.198:/home/student/Data/cit225/mysql .

After entering the password for the student on the Linux VM, you should see the following copy over:

Raiders2.png              | 99 kB |  99.5 kB/s | ETA: 00:00:00 | 100%
LordOfTheRings3.png       | 119 kB | 119.8 kB/s | ETA: 00:00:00 | 100%
HarryPotter4.png          | 103 kB | 103.9 kB/s | ETA: 00:00:00 | 100%
Raiders1.png              | 92 kB |  92.4 kB/s | ETA: 00:00:00 | 100%
Raiders3.png              | 123 kB | 123.9 kB/s | ETA: 00:00:00 | 100%
LordOfTheRings2.png       | 111 kB | 111.7 kB/s | ETA: 00:00:00 | 100%
LordOfTheRings1.png       | 103 kB | 104.0 kB/s | ETA: 00:00:00 | 100%
HarryPotter2.png          | 118 kB | 118.7 kB/s | ETA: 00:00:00 | 100%
HarryPotter7.png          | 150 kB | 150.2 kB/s | ETA: 00:00:00 | 100%
HarryPotter3.png          | 106 kB | 106.1 kB/s | ETA: 00:00:00 | 100%
HarryPotter5.png          | 82 kB |  82.5 kB/s | ETA: 00:00:00 | 100%
HarryPotter6.png          | 129 kB | 129.9 kB/s | ETA: 00:00:00 | 100%
HarryPotter1.png          | 118 kB | 118.8 kB/s | ETA: 00:00:00 | 100%
HarryPotter8.png          | 150 kB | 150.9 kB/s | ETA: 00:00:00 | 100%
HarryPotter8.txt          | 8 kB |   8.5 kB/s | ETA: 00:00:00 | 100%
HarryPotter3.txt          | 5 kB |   5.8 kB/s | ETA: 00:00:00 | 100%
HarryPotter5.txt          | 7 kB |   7.9 kB/s | ETA: 00:00:00 | 100%
HarryPotter1.txt          | 6 kB |   6.6 kB/s | ETA: 00:00:00 | 100%
HarryPotter2.txt          | 7 kB |   7.8 kB/s | ETA: 00:00:00 | 100%
Raiders3.txt              | 5 kB |   5.6 kB/s | ETA: 00:00:00 | 100%
HarryPotter4.txt          | 7 kB |   7.5 kB/s | ETA: 00:00:00 | 100%
HarryPotter7.txt          | 5 kB |   5.4 kB/s | ETA: 00:00:00 | 100%
HarryPotter6.txt          | 7 kB |   7.4 kB/s | ETA: 00:00:00 | 100%
LOTRFellowship.txt        | 4 kB |   5.0 kB/s | ETA: 00:00:00 | 100%
apply_store_base.sql      | 1 kB |   1.6 kB/s | ETA: 00:00:00 | 100%
query_membership.sql      | 0 kB |   0.3 kB/s | ETA: 00:00:00 | 100%
apply_mysql_lab1.sql      | 1 kB |   1.9 kB/s | ETA: 00:00:00 | 100%
configure_mysql_web.sql   | 37 kB |  37.1 kB/s | ETA: 00:00:00 | 100%
seed_mysql_store_ri2.sql  | 58 kB |  58.5 kB/s | ETA: 00:00:00 | 100%
cleanup_mysql_store.sql   | 5 kB |   5.4 kB/s | ETA: 00:00:00 | 100%
create_mysql_store_ri2.sq | 21 kB |  21.1 kB/s | ETA: 00:00:00 | 100%

My students will need to repeat this step to transfer all of the sample PHP files that demonstrate web application patterns. They also need to inspect individual files to ensure any path referencing commands are manually converted to their new Windows equivalent.

They can move the physical files as the root superuser with the following pscp command provide you haven’t stored the files somewhere other than the default location:

C:\Data\temp>pscp -r root@192.168.147.198:/var/lib/mysql .

As always, I hope this helps those trying to sort things out.

Written by maclochlainn

May 3rd, 2020 at 11:58 am

Java & MySQL 8.0.19

without comments

It’s the in-between term time and we’re all stuck at home. I decided to update the image for my Fedora 30 virtual machine. I had a work around to the update issue that I had encountered last October in Bug #96969 but it was not required with the current version. However, after updating from MySQL 8.0.17 to MySQL 8.0.19, I found that my Java connection example failed.

The $CLASSPATH value was correct:

/usr/share/java/mysql-connector-java.jar:.

The first error that I got was the my reference to MySQL JDBC driver was incorrect. The error message is quite clear:

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
Cannot connect to database server:
The server time zone value 'MDT' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

I changed the MySQL Driver reference as instructed by the error message:

29
30
31
      // Create instance of MySQLDriver.
      Class.forName ("com.mysql.cj.jdbc.Driver").newInstance();
      conn = DriverManager.getConnection (url, username, password);

After the change, I got the following error while retesting my little MySQL Java driver connection test program. Initially, I thought this required a change in the Java environment but that wasn’t it.

Cannot connect to database server:
The server time zone value 'MDT' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

It required me to add the following line to my /etc/my.cnf configuration file, which synchronizes the database’s timezone with the operating system.

# Synchronize the MySQL clock with the computer system clock.
default-time-zone='+00:00'

Then, running my MySQL Driver connection test program worked like a charm. It returns the following:

Database connection established
MySQLDriver Version [8.0.19]
Database connection terminated

Here’s the MySQL Connector Java code if you’d like to use the MySQLDriver.java file:

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// Import classes.
import java.sql.*;
 
/* You can't include the following on Linux without raising an exception. */
// import com.mysql.jdbc.Driver;
 
public class MySQLDriver {
  public MySQLDriver() {
    /* Declare variables that require explicit assignments because
       they're addressed in the finally block. */
    Connection conn = null;
    Statement stmt = null;
    ResultSet rset = null;
 
    /* Declare other variables. */
    String url;
    String username = "student";
    String password = "student";
    String database = "studentdb";
    String hostname = "localhost";
    String port = "3306";
    String sql;
 
    /* Attempt a connection. */
    try {
      // Set URL.
      url = "jdbc:mysql://" + hostname + ":" + port + "/" + database;
 
      // Create instance of MySQLDriver.
      Class.forName ("com.mysql.cj.jdbc.Driver").newInstance();
      conn = DriverManager.getConnection (url, username, password);
 
      // Query the version of the database.
      sql = "SELECT version()";
      stmt = conn.createStatement();
      rset = stmt.executeQuery(sql);
 
      System.out.println ("Database connection established");
 
      // Read row returns for one column.
      while (rset.next()) {
        System.out.println("MySQLDriver Version [" + rset.getString(1) + "]"); }
 
    }
    catch (SQLException e) {
      System.err.println ("Cannot connect to database server:");
      System.out.println(e.getMessage());
    }
    catch (ClassNotFoundException e) {
      System.err.println ("Cannot find MySQL driver class:");
      System.out.println(e.getMessage());
    }
    catch (InstantiationException e) {
      System.err.println ("Cannot instantiate class:");
      System.out.println(e.getMessage());
    }
    catch (IllegalAccessException e) {
      System.err.println ("Illegal access exception:");
      System.out.println(e.getMessage());
    }
    finally {
      if (conn != null) {
        try {
          rset.close();
          stmt.close();
          conn.close();
          System.out.println ("Database connection terminated");
        }
        catch (Exception e) { /* ignore close errors */ }
      }
    }
  }
  /* Unit test. */
  public static void main(String args[]) {
    new MySQLDriver();
  }
}

As always, I hope this helps those who encounter similar problems.

Written by maclochlainn

April 10th, 2020 at 12:42 pm

Session Variables

without comments

In MySQL and Oracle, you set a session variable quite differently. That means you should expect there differences between setting a session variable in Postgres. This blog post lets you see how to set them in all three databases. I’m always curious what people think but I’m willing to bet that MySQL is the simplest approach. Postgres is a bit more complex because you must use a function call, but Oracle is the most complex.

The difference between MySQL and Postgres is an “@” symbol versus a current_setting() function call. Oracle is more complex because it involves the mechanics in Oracle’s sqlplus shell, SQL dialect, and PL/SQL language (required to assign a value to a variable).

MySQL

MySQL lets you declare a session variable in one step and use it one way in a SQL statement or stored procedure.

  1. You set a session variable on a single line with the following command:

    SET @my_variable_name := 'My Value';

  2. You can query a variable from the pseudo table dual or as a comparison value in the SELECT-list

    SELECT @my_variable_name AS "The Value" FROM dual;

    or WHERE clause

    SELECT column_name
    FROM   table_name
    WHERE  column_name = @my_variable_name;

Postgres

Postgres lets you declare a session variable in one step and use it one way in a SQL statement or stored procedure.

  1. You set a session variable in a single line. It iss critical to note that you must use double quotes around the session variable name and single quotes for the value. You raise an error when you use a single quote instead a double quote around the session variable name. The syntax is:

    SET SESSION "videodb.table_name" = 'new_hire';

  2. You can query a variable from the pseudo table dual or as a comparison value in the SELECT-list with the current_setting() function call.

    SELECT current_setting('videodb.table_name') AS "The Value";

    or WHERE clause

    SELECT column_name
    FROM   table_name
    WHERE  column_name = current_setting('videodb.table_name');

Oracle

There are two steps required to declare a session variable in Oracle. First, you need to define the variable in the SQL*Plus session. Oracle lets you define a variable like you would define a variable in the C language, using extern before the variable’s type. Second, you assign a value to the session variable in an anonymous PL/SQL block. There is no single line statement to declare a variable with an initial value.

  1. You set a session variable by using the VARIABLE keyword, a variable name, and data type. The supported data types are: BLOB, BFILE, BINARY_DOUBLE, BINARY_FLOAT, CHAR, CLOB, NCHAR, NCLOB, NVARCHAR2, REFCURSOR, and VARCHAAR2. You define a variable with the following syntax:

    VARIABLE bv_variable_name VARCHAR2(30)

  2. You assign a value to the bind variable inside an anonymous block by prefacing the variable name with a colon. You assign values inside PL/SQL with the walrus operator (:=) and a string enclosed by single quotes. Anonymous blocks start with a BEGIN and end with an END followed by a semicolon (;) and a forward slash (/) to dispatch the block for execution. The following example shows a full block:

    BEGIN
      :bv_variable_name := 'Some Value';
    END;
    /

  3. You can query any declared variable from the pseudo table dual or as a comparison value in the SELECT-list

    SELECT :bv_variable_name FROM dual;

    or WHERE clause

    SELECT column_name
    FROM   table_name
    WHERE  column_name = :bv_variable_name;

Written by maclochlainn

September 28th, 2019 at 9:01 pm

mysqli Strict Standards

with 2 comments

Six years ago I wrote a common lookup post to illustrate the effectiveness of things used throughout your applications. Now, I’m updating my student image with a more complete solution to show how to avoid update anomalies.

In the prior post, I used a while loop in PHP, like the following:

do {
      ...
} while($stmt->next_result());

Using PHP Version 7.3.8 and MySQL 8.0.16, that now raises the following error message:

Strict Standards: mysqli_stmt::next_result(): There is no next result set. Please, call mysqli_stmt_more_results()/mysqli_stmt::more_results() to check whether to call this function/method in /var/www/html/app/library.inc on line 81

You can see this type of error when you set the following parameters in your file during testing:

ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(E_ALL);

You can read more about error handling at this web page. The new and strict compliance standard for mysqli managing rows is:

do {
      ...
} while($stmt->more_result());

As always, I hope this helps those looking for an answer.

Written by maclochlainn

September 14th, 2019 at 10:30 pm

Posted in LAMP,MySQL,MySQL 8,mysqli,PHP

Tagged with ,

MySQL Update in mysqli

without comments

Somebody didn’t like the MySQLi Update Query example on the tutorialspoint.com website because it use the procedure mysqli_query style. Here’s a simple example of using the object-oriented method version. More or less, instead of query it uses the more intuitive execute() method.

The update_member function contains the logic and below it is a call to the test the function. It relies on a MySQLCredentials.inc file that contains the hostname, user name, password, and database name. You can create create member table, like my example in MySQL 8, or any other table in your MySQL database.

<?php
/*
||  Function Name: update_member
*/
function update_member($account_number, $member_type, $credit_card_number, $credit_card_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();
 
    /* Disabling auto commit when you want two or more statements executed as a set.
    || ------------------------------------------------------------
    ||  You would add the following command to disable the default
    ||  of auto commit.
    ||  ------------------------------
    ||   $mysqli->autocommit(FALSE);
    || ------------------------------------------------------------
    */
 
    // Declare a static query.
    $sql = "UPDATE   member\n"
         . "SET      member_type = ?\n"
         . ",        credit_card_number = ?\n"
         . ",        credit_card_type = ?\n"
         . "WHERE    account_number = ?\n";
 
    /* Prepare statement.
    || ------------------------------------------------------------
    ||  Please note that the bind_param method is a position 
    ||  rather than named notation, which means you must provide
    ||  the variables in the same order as they are found in
    ||  the defined $sql variable as "?".
    || ------------------------------------------------------------
    ||  print($sql);
    ||  print("Member Type:      [1][".$member_type."]\n");
    ||  print("Credit Card No:   [2][".$credit_card_number."]\n");
    ||  print("Credit Card Type: [3][".$credit_card_type."]\n");
    ||  print("Account Number:   [4][".$account_number."]\n");
    || ------------------------------------------------------------
    */
    if ($stmt->prepare($sql)) {
      $stmt->bind_param("ssss",$member_type,$credit_card_number,$credit_card_type,$account_number); } 
 
    // Attempt query and exit with failure before processing.
    if (!$stmt->execute()) {
 
      // 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();
      || ------------------------------------------------------------
      */
    }
  }
}
 
// Test case
update_member('US00011', '1006', '6011-0000-0000-0078', '1007');
?>

I put this logic in a function.php file. If you do the same, you can run the test case like this from the command line:

php function.sql

As always, I hope this helps.

Written by maclochlainn

September 14th, 2019 at 6:20 pm

Python MySQL Query

without comments

Somebody asked me how to expand a prior example with the static variables so that it took arguments at the command line for the variables. This example uses Python 3 new features in the datetime package.

There’s a small trick converting the string arguments to date data types. Here’s a quick example that shows you how to convert the argument list into individual date data type variables:

#!/usr/bin/python3
 
# include standard modules
import sys
from datetime import datetime
 
# Capture argument list.
fullCmdArguments = sys.argv
 
# Assignable variables.
beginDate = ""
endDate = ""
 
# Assign argument list to variable.
argumentList = fullCmdArguments[1:]
 
# Enumerate through the argument list where beginDate precedes endDate as strings.
try:
  for i, s in enumerate(argumentList):
    if (i == 0):
      beginDate = datetime.date(datetime.fromisoformat(s))
    elif (i == 1):
      endDate = datetime.date(datetime.fromisoformat(s))
except ValueError:
  print("One of the first two arguments is not a valid date (YYYY-MM-DD).")
 
# Print the processed values and types.
print("Begin Date: [",beginDate,"][",type(beginDate),"]")
print("End Date:   [",endDate,"][",type(endDate),"]")

Assume you call this arguments.py. Then, you call it with valid conforming date format value like the following command-line example:

./arguments.py 2001-01-01 2003-12-31

It returns the arguments after they have been converted to date data types. The results should look like this:

Begin Date:  1991-01-01 [ <class 'datetime.date'> ]
End Date:    2004-12-31 [ <class 'datetime.date'> ]

The next Python example accepts dynamic arguments at the command line to query the MySQL database:

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#!/usr/bin/python3
 
# Import the library.
import sys
import mysql.connector
from datetime import datetime
from datetime import date
from mysql.connector import errorcode
 
# Capture argument list.
fullCmdArguments = sys.argv
 
# Assignable variables.
start_date = ""
end_date = ""
 
# Assign argument list to variable.
argumentList = fullCmdArguments[1:]
 
#  Check and process argument list.
# ============================================================
#  If there are less than two arguments provide default values.
#  Else enumerate and convert strings to dates.
# ============================================================
if (len(argumentList) < 2):
  # Set a default start date.
  if (isinstance(start_date,str)):
    start_date = date(1980, 1, 1)
 
  # Set the default end date.
  if (isinstance(end_date,str)):
    end_date = datetime.date(datetime.today())
else:
  # Enumerate through the argument list where beginDate precedes endDate as strings.
  try:
    for i, s in enumerate(argumentList):
      if (i == 0):
        start_date = datetime.date(datetime.fromisoformat(s))
      elif (i == 1):
        end_date = datetime.date(datetime.fromisoformat(s))
  except ValueError:
    print("One of the first two arguments is not a valid date (YYYY-MM-DD).")
 
#  Attempt the query.
# ============================================================
#  Use a try-catch block to manage the connection.
# ============================================================
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student', password='student',
                                host='127.0.0.1',
                                database='studentdb')
  # Create cursor.
  cursor = cnx.cursor()
 
  # Set the query statement.
  query = ("SELECT CASE "
           "         WHEN item_subtitle IS NULL THEN item_title "
           "         ELSE CONCAT(item_title,': ',item_subtitle) "
           "         END AS title, "
           "release_date "
           "FROM item "
           "WHERE release_date BETWEEN %s AND %s "
           "ORDER BY item_title")
 
  # Execute cursor.
  cursor.execute(query, (start_date, end_date))
 
  # Display the rows returned by the query.
  for (item_name, release_date) in cursor:
    print("{}, {:%d-%b-%Y}".format(item_name, release_date))
 
#  Handle exception and close connection.
# ============================================================
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print("Error code:", e.errno)        # error number
    print("SQLSTATE value:", e.sqlstate) # SQLSTATE value
    print("Error message:", e.msg)       # error message
 
# Close the connection when the try block completes.
finally:
  cnx.close()

You can call the python-mysql-query.py program with the following syntax:

./python-mysql-query.py 2001-01-01 2003-12-31

It returns the films between 1 Jan 2001 and 31 Dec 2003, like this:

Clear and Present Danger: Special Collector's Edition, 06-May-2003
Die Another Day: 2-Disc Ultimate Version, 03-Jun-2003
Die Another Day, 03-Jun-2003
Die Another Day, 03-Jun-2003
Golden Eye, 03-Jun-2003
Golden Eye: Special Edition, 03-Jun-2003
Harry Potter and the Chamber of Secrets, 28-May-2002
Harry Potter and the Chamber of Secrets: Two-Disc Special Edition, 28-May-2002
Harry Potter and the Sorcerer's Stone, 28-May-2002
Harry Potter and the Sorcerer's Stone: Two-Disc Special Edition, 28-May-2002
Harry Potter and the Sorcerer's Stone: Full Screen Edition, 28-May-2002
MarioKart: Double Dash, 17-Nov-2003
Pirates of the Caribbean, 30-Jun-2003
RoboCop, 24-Jul-2003
Splinter Cell: Chaos Theory, 08-Apr-2003
Star Wars II: Attack of the Clones, 16-May-2002
Star Wars II: Attack of the Clones, 16-May-2002
The Chronicles of Narnia: The Lion, the Witch and the Wardrobe, 30-Jun-2003
The Chronicles of Narnia: The Lion, the Witch and the Wardrobe, 16-May-2002

As always, I hope this helps somebody who wants to learn how to use Python with the MySQL database.

Written by maclochlainn

September 6th, 2019 at 10:31 pm

MySQL Python Connector

with one comment

While building my student image on Fedora 30, I installed the MySQL PHP Connector (php-mysqlndrp) but neglected to install the Python Connector. This adds the installation and basic test of the Python Connector to the original blog post.

You use the following command with a wildcard as a privileged user. The wildcard is necessary because you need to load two libraries to support Python 2.7 and 3.7, which are installed on Fedora 30. You also need to be the root user or a user that is found in the sudoer’s list:

yum install -y mysql-connector-python*

Leveraging the MySQL Connector/Python Coding Examples documentation, Section 5.1 Connecting to MySQL Using Connector/Python here’s a test of the connection to MySQL 8.

# Import the library.
import mysql.connector
from mysql.connector import errorcode
 
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student', password='student',
                                host='127.0.0.1',
                                database='studentdb')
 
  # Print the value.
  print("Database connection resolved.")
 
# Handle exception and close connection.
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print(e)
 
# Close the connection when the try block completes.
else:
  cnx.close()

Leveraging the MySQL Connector/Python Coding Examples documentation, Section 5.4 Querying Data Using Connector/Python here’s a test of the connection to MySQL 8.

# Import the library.
import datetime
import mysql.connector
from mysql.connector import errorcode
 
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student', password='student',
                                host='127.0.0.1',
                                database='studentdb')
  # Create cursor.
  cursor = cnx.cursor()
 
  # Set the query statement.
  query = ("SELECT "
           "CASE "
           "  WHEN item_subtitle IS NULL THEN item_title "
           "  ELSE CONCAT(item_title,': ',item_subtitle) "
           "END AS title, "
           "release_date "
           "FROM item "
           "WHERE release_date BETWEEN %s AND %s "
           "ORDER BY item_title")
 
  # Set the start and end date.
  start_date = datetime.date(1991, 1, 1)
  end_date = datetime.date(2004, 12, 31)
 
  # Execute cursor.
  cursor.execute(query, (start_date, end_date))
 
  # Display the rows returned by the query.
  for (item_name, release_date) in cursor:
    print("{}, {:%d %b %Y}".format(item_name, release_date))
 
  # Close cursor.
  cursor.close()
 
# ------------------------------------------------------------
# Handle exception and close connection.
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print "Error code:", e.errno        # error number
    print "SQLSTATE value:", e.sqlstate # SQLSTATE value
    print "Error message:", e.msg       # error message
 
# Close the connection when the try block completes.
else:
  cnx.close()

If you run the above in Python 2.7 it works fine. It fails to parse successfully in Python 3.x because the print() function requires the parentheses all the time. You would need to re-write the except block, like this with the parentheses:

# Handle exception and close connection.
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print("Error code:", e.errno)        # error number
    print("SQLSTATE value:", e.sqlstate) # SQLSTATE value
    print("Error message:", e.msg)       # error message

While it works without the parentheses in Python 2.7, it also works with the parentheses. That means the best practice is to write cross compatible code by always using the parentheses with the print() function.

As always, I hope this helps somebody.j

Written by maclochlainn

August 21st, 2019 at 1:44 am