MacLochlainns Weblog

Michael McLaughlin's Technical Blog

Site Admin

Archive for the ‘Oracle’ Category

PL/SQL Fall Through?

with 2 comments

Somebody wants to know how you can write a PL/SQL solution that mimics the fall through of a switch statement because PL/SQL doesn’t support a switch statement (it does support a simple and searched CASE statement without fall through). It’s a question that I found interesting because there wasn’t a need for it when I figured out what he wanted to accomplish. Essentially, he wanted to know how to implement a nested loop where the first loop runs in ascending order and the nested loop runs in descending order based on the value of the outer loop.

While it seems Christmas songs aren’t politically correct, The Twelve Days of Christmas lets me show you how to implement a coupled nested loop. The easiest way to implement a solution requires an object type, like

1
2
3
4
5
CREATE OR REPLACE
  TYPE lyric IS OBJECT
  ( day_name   VARCHAR2(8)
  , gift_name  VARCHAR2(24));
/

The following anonymous block program shows you how to couple the performance of nested loops to print the lyrics from two collections:

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
DECLARE
  /* Declare an array of days and gifts. */
  TYPE days IS TABLE OF VARCHAR2(8);
  TYPE gifts IS TABLE OF lyric;
 
  /* Initialize the collection of days. */                    
  lv_days DAYS := days( 'first', 'second', 'third', 'fourth'
                      , 'fifth', 'sixth', 'seventh', 'eighth'
                      , 'nineth', 'tenth', 'eleventh', 'twelfth');
 
  /* Initialize the collection of lyrics. */
  lv_gifts GIFTS := gifts( lyric('and a', 'Partridge in a Pear Tree')
                         , lyric('Two', 'Turtle Doves')
                         , lyric('Three', 'French Hens')
                         , lyric('Four', 'Calling Birds')
                         , lyric('Five', 'Golden Rings' )
                         , lyric('Six', 'Geese a Laying')
                         , lyric('Seven', 'Swans a Swimming')
                         , lyric('Eight', 'Maids a Milking')
                         , lyric('Nine', 'Maids a Milking')
                         , lyric('Ten', 'Lords a Leaping')
                         , lyric('Eleven', 'Pipers Piping')
                         , lyric('Twelve', 'Drummers Drumming'));
BEGIN
  /* Read forward through the days. */
  FOR i IN 1..lv_days.COUNT LOOP
    dbms_output.put_line('On the ' || lv_days(i) || ' day of Christmas');
    dbms_output.put_line('my true love sent to me:');
 
    /* Read backward through the lyrics based on the ascending value of the day. */   
    FOR j IN REVERSE 1..i LOOP
      IF i = 1 THEN
        dbms_output.put_line('-'||'A'||' '||lv_gifts(j).gift_name);
      ELSE
        dbms_output.put_line('-'||lv_gifts(j).day_name||' '||lv_gifts(j).gift_name);
      END IF;
    END LOOP;
 
    /* A line break by verse. */
    dbms_output.put_line(CHR(10));
  END LOOP; 
END;
/

The FOR loop on line 31 descends from the current index of the ascending out loop. This shows you how to couple the performance of outer and inner loops. It let’s you print The Twelve Days of Christmas, as:

On the first day of Christmas
my true love sent to me:
-A Partridge in a Pear Tree
 
 
On the second day of Christmas
my true love sent to me:
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the third day of Christmas
my true love sent to me:
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the fourth day of Christmas
my true love sent to me:
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the fifth day of Christmas
my true love sent to me:
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the sixth day of Christmas
my true love sent to me:
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the seventh day of Christmas
my true love sent to me:
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the eighth day of Christmas
my true love sent to me:
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the nineth day of Christmas
my true love sent to me:
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the tenth day of Christmas
my true love sent to me:
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the eleventh day of Christmas
my true love sent to me:
-Eleven Pipers Piping
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the twelfth day of Christmas
my true love sent to me:
-Twelve Drummers Drumming
-Eleven Pipers Piping
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree

My conclusion is that the PL/SQL language doesn’t need to support fall through because it provides a simpler and more effective solution with coupled nested loops. As always, I hope the example helps those interested in a solution.

Written by maclochlainn

January 18th, 2015 at 12:13 am

Convert to SQL Server?

with 2 comments

I’m always amazed at the questions that pop up for me. For example, how do you convert an Oracle script that creates my Video Store model to a Microsoft SQL Server script. It’s not very hard but there’s one big caveat, and that’s the fact that system_user is a reserved word. That means you can’t create the Access Control List (ACL) table with a system_user name. The alternative, would be to convert the system_user table name to database_user. That’s what I’ve done in this example.

It’s also important to note that this example uses Microsoft SQL Server’s sqlcmd in batch mode. Naturally, it presumes that you’ve created a student user with a trivial password of student, and a studentdb schema. Also, that you’ve granted privileges so everything works (if you need help on that check my earlier post on how to setup a studentdb schema).

The following is an example of conditionally dropping and then creating a system_user table in an Oracle schema. It uses a CASCADE CONSTRAINTS clause to eliminate dependencies with foreign key values.

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
-- Conditionally drop the table and sequence.
BEGIN
  FOR i IN (SELECT NULL
            FROM   user_tables
            WHERE  TABLE_NAME = 'SYSTEM_USER') LOOP
    EXECUTE IMMEDIATE 'DROP TABLE system_user CASCADE CONSTRAINTS';
  END LOOP;
  FOR i IN (SELECT NULL
            FROM   user_sequences
            WHERE  sequence_name = 'SYSTEM_USER_S1') LOOP
    EXECUTE IMMEDIATE 'DROP SEQUENCE system_user_s1';
  END LOOP;
END;
/
 
--  Create SYSTEM_USER table.
CREATE TABLE system_user
( system_user_id            NUMBER        CONSTRAINT system_user_pk PRIMARY KEY
, system_user_name          VARCHAR2(20)  CONSTRAINT system_user_nn1 NOT NULL
, system_user_group_id      NUMBER        CONSTRAINT system_user_nn2 NOT NULL
, system_user_type          NUMBER        CONSTRAINT system_user_nn3 NOT NULL
, first_name                VARCHAR2(20)
, middle_name               VARCHAR2(20)
, last_name                 VARCHAR2(20)
, created_by                NUMBER        CONSTRAINT system_user_nn4 NOT NULL
, creation_date             DATE          CONSTRAINT system_user_nn5 NOT NULL
, last_updated_by           NUMBER        CONSTRAINT system_user_nn6 NOT NULL
, last_update_date          DATE          CONSTRAINT system_user_nn7 NOT NULL
, CONSTRAINT system_user_fk1  FOREIGN KEY (created_by)
  REFERENCES system_user (system_user_id)
, CONSTRAINT system_user_fk2  FOREIGN KEY (last_updated_by)
  REFERENCES system_user (system_user_id));
 
-- Create SYSTEM_USER_S1 sequence with a start value of 1001.
CREATE SEQUENCE system_user_s1 START WITH 1001;
 
-- Conditionally drop the table and sequence.
BEGIN
  FOR i IN (SELECT NULL
            FROM   user_tables
            WHERE  TABLE_NAME = 'COMMON_LOOKUP') LOOP
    EXECUTE IMMEDIATE 'DROP TABLE common_lookup CASCADE CONSTRAINTS';
  END LOOP;
  FOR i IN (SELECT NULL
            FROM   user_sequences
            WHERE  sequence_name = 'COMMON_LOOKUP_S1') LOOP
    EXECUTE IMMEDIATE 'DROP SEQUENCE common_lookup_s1';
  END LOOP;
END;
/
 
--  Create COMMON_LOOKUP table.
CREATE TABLE common_lookup
( common_lookup_id            NUMBER
, common_lookup_context       VARCHAR2(30) CONSTRAINT nn_clookup_1 NOT NULL
, common_lookup_type          VARCHAR2(30) CONSTRAINT nn_clookup_2 NOT NULL
, common_lookup_meaning       VARCHAR2(30) CONSTRAINT nn_clookup_3 NOT NULL
, created_by                  NUMBER       CONSTRAINT nn_clookup_4 NOT NULL
, creation_date               DATE         CONSTRAINT nn_clookup_5 NOT NULL
, last_updated_by             NUMBER       CONSTRAINT nn_clookup_6 NOT NULL
, last_update_date            DATE         CONSTRAINT nn_clookup_7 NOT NULL
, CONSTRAINT pk_c_lookup_1    PRIMARY KEY(common_lookup_id)
, CONSTRAINT fk_c_lookup_1    FOREIGN KEY(created_by) REFERENCES system_user(system_user_id)
, CONSTRAINT fk_c_lookup_2    FOREIGN KEY(last_updated_by) REFERENCES system_user(system_user_id));
 
-- Create a non-unique index on a single column.
CREATE INDEX common_lookup_n1
  ON common_lookup(common_lookup_context);
 
-- Create a unique index based on two columns.
CREATE UNIQUE INDEX common_lookup_u2
  ON common_lookup(common_lookup_context,common_lookup_type);
 
-- Create COMMON_LOOKUP_S1 sequence with a start value of 1001.
CREATE SEQUENCE common_lookup_s1 START WITH 1001;

You can do the same thing for a database_user table in Microsoft SQL Server with the following syntax. Unfortunately, there isn’t a CASCADE CONSTRAINTS clause that we can append in Microsoft SQL Server. The script uses a dynamic SQL statement with a Common Table Expression (CTE) to generate a list of ALTER statements that drop foreign key constraints in the schema.

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
/* Drop all foreign keys. */
USE studentdb;
 
/* Create a session variable to hold a command list. */
SELECT 'Create a session variable.' AS "Statement";
DECLARE @SQL NVARCHAR(MAX) = N'';
 
/* Generate the command list to drop foreign key constraints. */
SELECT 'Generate dynamic SQL statements.' AS "Statement";
;WITH x AS
(SELECT N'ALTER TABLE ' +
          OBJECT_SCHEMA_NAME(parent_object_id) + N'.' +
          OBJECT_NAME(parent_object_id) + N' ' +
        N'DROP CONSTRAINT ' + name + N';' AS sqlstmt
 FROM     sys.foreign_keys)
SELECT @SQL += sqlstmt FROM x;
 
/* Call the dynamically generated statements. */
SELECT 'Execute dynamic SQL statements.' AS "Statement";
EXEC sp_executesql @SQL;
 
/* Conditionally drop tables. */
SELECT 'Conditionally drop studentdb.common_lookup table.' AS "Statement";
IF OBJECT_ID('studentdb.database_user','U') IS NOT NULL
  DROP TABLE studentdb.database_user;
 
/* Create a table with self-referencing foreign key constraints. */
SELECT 'Create studentdb.common_lookup table.' AS "Statement";
CREATE TABLE studentdb.database_user
( database_user_id        INT          NOT NULL IDENTITY(1,1) CONSTRAINT database_user_pk PRIMARY KEY
, database_user_name      VARCHAR(20)  NOT NULL
, database_user_group_id  INT          NOT NULL
, database_user_type      INT          NOT NULL
, first_name              VARCHAR(20)
, middle_name             VARCHAR(20)
, last_name               VARCHAR(20)
, created_by              INT          NOT NULL
, creation_date           DATE         NOT NULL
, last_updated_by         INT          NOT NULL
, last_update_date        DATE         NOT NULL
, CONSTRAINT database_user_fk1 FOREIGN KEY (created_by)
  REFERENCES studentdb.database_user (database_user_id)
, CONSTRAINT database_user_fk2 FOREIGN KEY (created_by)
  REFERENCES studentdb.database_user (database_user_id));
 
/* Conditionally drop common_lookup table. */
SELECT 'Conditionally drop studentdb.common_lookup table.' AS "Statement";
IF OBJECT_ID('studentdb.common_lookup','U') IS NOT NULL
  DROP TABLE studentdb.common_lookup;
 
/* Create a table with external referencing foreign key constraints. */  
SELECT 'Create studentdb.common_lookup table.' AS "Statement";
CREATE TABLE studentdb.common_lookup
( common_lookup_id            INT          NOT NULL  IDENTITY(1,1) CONSTRAINT common_lookup_pk PRIMARY KEY
, common_lookup_context       VARCHAR(30)  CONSTRAINT nn_clookup_1 NOT NULL
, common_lookup_type          VARCHAR(30)  CONSTRAINT nn_clookup_2 NOT NULL
, common_lookup_meaning       VARCHAR(30)  CONSTRAINT nn_clookup_3 NOT NULL
, created_by                  INT          CONSTRAINT nn_clookup_4 NOT NULL
, creation_date               DATE         CONSTRAINT nn_clookup_5 NOT NULL
, last_updated_by             INT          CONSTRAINT nn_clookup_6 NOT NULL
, last_update_date            DATE         CONSTRAINT nn_clookup_7 NOT NULL
, CONSTRAINT common_lookup_fk1 FOREIGN KEY(created_by)
  REFERENCES studentdb.database_user (database_user_id)
, CONSTRAINT common_lookup_fk2 FOREIGN KEY(last_updated_by)
  REFERENCES studentdb.database_user (database_user_id));

You can run it from a file by calling the sqlcmd utility. You’ll need to know several things to run it. First, you need to know your database instance. You can capture that from a query against the data dictionary or catalog. Just run the following from inside the Microsoft SQL Server Management Studio (SSMS):

SELECT @@SERVERNAME;

In my case, it shows the following, which is the machine’s hostname a backslash and SQLEXPRESS:

MCLAUGHLINSQL\SQLEXPRESS

The script uses sqltest.sql as a file name, and you can call it from the Windows shell environment like this:

sqlcmd -S MCLAUGHLINSQL\SQLEXPRESS -U student -P student -i C:\Data\MicrosoftSQL\sqltest.sql -o C:\Data\Microsoft\sqltest.out

As always, I hope this helps.

Written by maclochlainn

January 15th, 2015 at 7:18 pm

Querying an Object Type

without comments

I demonstrated a number of SQL approaches to reading object types in Appendix B of the Oracle Database 12c PL/SQL Programming book. For example, the easiest one to construct and return the results from a TO_STRING member function uses the TREAT function:

SELECT TREAT(base_t() AS base_t).to_string() AS "Text"
FROM   dual;

However, it seems that I could have provided one more. Here’s an example of how you can test the construction of an object type and how you can return its attributes with a query. It’s important to note that there’s a natural problem with this syntax when you increment a sequence inside the object type. The problem is that it double increments the counter for the sequence.

SELECT *
FROM   TABLE(SELECT CAST(COLLECT(base_t()) AS base_t_tab)
             FROM dual);

The syntax for the COLLECT function requires that you put it inside a SELECT-list. Then, the CAST function converts a single instance of the BASE_T object type to a one element BASE_T_TAB collection. Finally, the TABLE function returns a single row from the BASE_T_TAB collection.

You can find a more complete article covering column substitutability and object types and subtypes on the ToadWorld site. I think it helps clear up how you can effectively write PL/SQL types and subtypes for persistent object type columns.

Written by maclochlainn

November 25th, 2014 at 12:33 am

Finding Direct Indexes

without comments

If you’re not using Toad DBA Suite, it’s sometimes hard to find solutions. Somebody wanted to know how to find indexes that aren’t indirect. Indirect indexes are those created for a primary key because a primary key column or set of columns are both not null and uniquely constrained. Likewise, you create a unique index when you can create a unique constraint. You can’t drop a unique index for a primary key without dropping the primary key or unique constraint that indirectly created it.

The following query returns indexes with one or more columns that are created by a CREATE INDEX statement on a target table. It excludes unique indexes created by a primary key constraint, and it returns the relative position of columns in an index:

COLUMN sequence_name   FORMAT A22 HEADING "Sequence Name"
COLUMN column_position FORMAT 999 HEADING "Column|Position"
COLUMN column_name     FORMAT A22 HEADING "Column|Name"
SELECT   ui.index_name
,        uic.column_position
,        uic.column_name
FROM     user_indexes ui INNER JOIN user_ind_columns uic
ON       ui.index_name = uic.index_name
AND      ui.table_name = uic.table_name
WHERE    ui.table_name = UPPER('&&table_name')
AND NOT  ui.index_name IN (SELECT constraint_name
                           FROM   user_constraints
                           WHERE  table_name = UPPER('&&table_name'))
ORDER BY ui.index_name
,        uic.column_position;

It can be rewritten into a function, which can then drop indexes based on a table name:

CREATE OR REPLACE FUNCTION drop_indexes_on
( pv_table_name  VARCHAR2 ) RETURN NUMBER IS 
 
  /* A return value. */
  lv_return  NUMBER := 0;
 
  /* A query to return only directly created indexes. */
  CURSOR find_indexes_on
  ( cv_table_name  VARCHAR2 ) IS
    SELECT   DISTINCT ui.index_name
    FROM     user_indexes ui INNER JOIN user_ind_columns uic
    ON       ui.index_name = uic.index_name
    AND      ui.table_name = uic.table_name
    WHERE    ui.table_name = UPPER(cv_table_name)
    AND NOT  ui.index_name IN (SELECT constraint_name
                               FROM   user_constraints
                               WHERE  table_name = UPPER(cv_table_name));
 
  /* Declare function autonomous. */
  PRAGMA AUTONOMOUS_TRANSACTION;
 
BEGIN
 
  /* Drop the indexes on a table. */
  FOR i IN find_indexes_on(pv_table_name) LOOP
    EXECUTE IMMEDIATE 'DROP INDEX '||i.index_name;
    lv_return := 1;
  END LOOP;
 
  RETURN lv_return;
END drop_indexes_on;
/

You can call the drop_on_indexes_on function like this:

SELECT   drop_indexes_on(UPPER('address_lab'))
FROM     dual;

Hope this helps those who need to work with dropping indexes.

Written by maclochlainn

November 23rd, 2014 at 8:42 pm

E-Business Customers

without comments

It seems the Oracle E-Business Suite stymies newbies. Naturally, it’s complex and requires some research before you try to develop any customization.

Having recently fielded a question about how to manage, search, create and update customers for a third party order entry system, I’m always surprised by how little people know about Oracle’s Trading Community Architecture (TCA). They likewise frequently don’t know that there is already a documented process, like the one defined in the Oracle Trading Community Architecture User Guide:

You also have the Oracle Trading Community Architecture Reference Guide, which provides more detailed information. I strongly recommend you read these before trying to Google a solution that may or may not meet your needs. Naturally, good PL/SQL coding skills make this type of activity straightforward. That’s why Oracle staff should master PL/SQL.

Written by maclochlainn

September 4th, 2014 at 11:25 am

Wrapping SQL*Plus

without comments

One annoying thing from installing Oracle Database 11g on Fedora, was that the up arrows for command history didn’t work. I decided to fix that today after seeing Lutz Hartmann’s article on rlwrap. Unfortunately, the epel (Extra Packages for Enterprise Linux) package he recommended doesn’t run on Fedora 20. You can read my tale of woe, or skip to the .bashrc function that fixed it when I installed only rlwrap.

Attempting it on yum, gave me these errors:

# yum install http://www.mirrorservice.org/sites/dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
Loaded plugins: langpacks, refresh-packagekit
epel-release-6-8.noarch.rpm                                 |  14 kB  00:00     
Examining /var/tmp/yum-root-5CLTPa/epel-release-6-8.noarch.rpm: epel-release-6-8.noarch
Marking /var/tmp/yum-root-5CLTPa/epel-release-6-8.noarch.rpm to be installed
Resolving Dependencies
--> Running transaction check
---> Package epel-release.noarch 0:6-8 will be installed
--> Processing Conflict: epel-release-6-8.noarch conflicts fedora-release
No package matched to upgrade: epel-release
--> Finished Dependency Resolution
Error: epel-release conflicts with fedora-release-20-3.noarch
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles –nodigest

Poking around for an epel fix wasn’t successful, so I chose to install only the rlwrap package. Here’s that command and log file:

[root@localhost ~]# yum install rlwrap 
Loaded plugins: langpacks, protectbase, refresh-packagekit
0 packages excluded due to repository protections
Resolving Dependencies
--> Running transaction check
---> Package rlwrap.x86_64 0:0.41-1.fc20 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
================================================================================
 Package         Arch            Version                 Repository        Size
================================================================================
Installing:
 rlwrap          x86_64          0.41-1.fc20             updates           95 k
 
Transaction Summary
================================================================================
Install  1 Package
 
Total download size: 95 k
Installed size: 204 k
Is this ok [y/d/N]: y
Downloading packages:
rlwrap-0.41-1.fc20.x86_64.rpm                               |  95 kB  00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction (shutdown inhibited)
  Installing : rlwrap-0.41-1.fc20.x86_64                                    1/1 
  Verifying  : rlwrap-0.41-1.fc20.x86_64                                    1/1 
 
Installed:
  rlwrap.x86_64 0:0.41-1.fc20                                                   
Complete!

The next step was getting it to work. A sqlplus function wrapper inside the .bashrc file seemed the easiest. Here’s the code to the .bashrc file:

# .bashrc
 
# Source global definitions
if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi
 
# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=
 
# User specific aliases and functions
. /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh
 
# Wrap sqlplus with rlwrap to edit prior lines.
sqlplus()
{
  if [ "$RLWRAP" = "0" ]; then
    sqlplus "$@"
  else
    rlwrap sqlplus "$@"
  fi
}
 
# Set vi as a command line editor.
set -o vi

As always, I hope this helps some folks.

Written by maclochlainn

August 20th, 2014 at 6:58 pm

Hiding a Java Source

with one comment

The ability to deploy Java inside the Oracle database led somebody to conclude that the source isn’t visible in the data catalog. Then, that person found that they were wrong because the Java source is visible when you use a DDL command to CREATE, REPLACE, and COMPILE the Java source. This post discloses how to find the Java source and how to prevent it from being stored in the data catalog.

You can verify that the Java class and source files exist with the following query:

1
2
3
4
5
6
7
8
COLUMN object_name FORMAT A20 HEADING "Object Name"
COLUMN object_type FORMAT A12 HEADING "Object Type"
COLUMN STATUS      FORMAT A14 HEADING "Object Status"
SELECT   object_name
,        object_type
,        STATUS
FROM     user_objects
WHERE    object_name = 'ReadFile';

It displays:

Object Name          Object Type  Object Status
-------------------- ------------ --------------
ReadFile             JAVA SOURCE  VALID
ReadFile             JAVA CLASS   VALID
 
2 rows selected.

Then, you can use the following query to discovery a Java library created by a SQL command:

1
2
3
4
5
6
COLUMN line FORMAT 9999 HEADING "Line|#"
COLUMN text FORMAT A66  HEADING "Text"
SELECT   line
,        text
FROM     user_source
WHERE    name = 'ReadFile';

It displays the following:

 Line # Text
------- ------------------------------------------------------------------
    1   // Java library imports.
    2   import java.io.File;
    3   import java.io.BufferedReader;
    4   import java.io.FileNotFoundException;
    5   import java.io.IOException;
    6   import java.io.FileReader;
    7   import java.security.AccessControlException;
    8
    9   // Class definition.
   10   public class ReadFile {
   11     // Define class variables.
   12     private static File file;
   13     private static FileReader inTextFile;
   14     private static BufferedReader inTextReader;
   15     private static StringBuffer output = new StringBuffer();
   16     private static String outLine, outText;
   17
   18     // Define readText() method.
   19     public static String readText(String fromFile)
   20       throws AccessControlException, IOException {
   21       // Read file.
   22       try {
   23         // Initialize File.
   24         file = new File(fromFile);
   25
   26         // Check for valid file.
   27         if (file.exists()) {
   28
   29           // Assign file to a stream.
   30           inTextFile = new FileReader(file);
   31           inTextReader = new BufferedReader(inTextFile);
   32
   33           // Read character-by-character.
   34           while ((outLine = inTextReader.readLine()) != null) {
   35             output.append(outLine + "\n"); }
   36
   37           // Assing the StringBuffer to a String.
   38           outText = Integer.toString(output.toString().length());
   39
   40           // Close File.
   41           inTextFile.close(); }
   42         else {
   43           outText = new String("Empty"); }}
   44       catch (IOException e) {
   45         outText = new String("");
   46         return outText; }
   47     return outText; }}
 
47 rows selected.

You can eliminate the source by compiling the Java library outside the database. Then, you use the loadjava utility to load the only the class file into the data catalog. The syntax would be the following command for an importer user in a video Pluggable Database (PDB):

loadjava -r -f -o -user importer/importer@video ReadFile.class

You should know that this syntax is disallowed by the loadjava utility, notwithstanding it’s found in the Oracle Database 12c documentation:

loadjava -r -f -o -user importer@video/importer ReadFile.class

You can verify that only the Java class file exists with the following query:

1
2
3
4
5
6
7
8
COLUMN object_name FORMAT A20 HEADING "Object Name"
COLUMN object_type FORMAT A12 HEADING "Object Type"
COLUMN STATUS      FORMAT A14 HEADING "Object Status"
SELECT   object_name
,        object_type
,        STATUS
FROM     user_objects
WHERE    object_name = 'ReadFile';

It displays:

Object Name          Object Type  Object Status
-------------------- ------------ --------------
ReadFile             JAVA CLASS   VALID
 
1 row selected.

Hope this helps those who want to hide the Java source files.

Written by maclochlainn

July 22nd, 2014 at 10:23 pm

External Table Access

without comments

I left to chance where students would attempt to place their external files in a Linux or Unix implementation. As frequently occurs, they choose a location in their student user’s home directory. Any attempt to read an external table based on a file in this type of directory fails because it’s not accessible by the Oracle user because the directory within the student user’s account isn’t reachable. You can’t simply chown a directory and the files in a directory.

The failure returns the following result:

SELECT COUNT(*) FROM transaction_upload
*
ERROR at line 1:
ORA-29913: error in executing ODCIEXTTABLEOPEN callout
ORA-29400: data cartridge error
error opening file /home/student/upload/transaction_upload.log

The reason isn’t readily visible to all, but a virtual directory must reference a physical directory owned by the oracle user and dba group. That also means the oracle user must own all directories from the logical mount point to the physical directory name.

Assuming you’re working in an Oracle Database 11g XE instance, you can create a valid upload directory by navigating to this directory:

/u01/app/oracle

Then, issue this command as the root user to create a new upload directory:

mkdir upload

Now you have the following directory:

/u01/app/oracle/upload

Assuming you’ve created the upload directory as the root user, the root user should issue the following two commands from the /u01/app/oracle directory:

chown -R oracle:dba upload
chmod -R 755 upload

Having made that change you should now be able to query the external file source, like a *.csv (comma-separated values) file. Hope this helps those trying to use external tables, which I subsequently wrote about for Toad World – External Tables.

Written by maclochlainn

June 19th, 2014 at 1:39 am

Sequence disallows order by

without comments

A call to a PRICE_S1 sequence in a query with an ORDER BY clause is disallowed, which typically occurs in an INSERT statement. Any attempt raises the following exception:

SELECT   price_s1.NEXTVAL AS price_id
                  *
ERROR at line 1:
ORA-02287: SEQUENCE NUMBER NOT allowed here

You need to remove the ORDER BY clause to eliminate the error.

Written by maclochlainn

June 15th, 2014 at 6:20 pm

SQL Insert from Query

with 5 comments

Sometimes my students find new errors that I’ve never seen. One student did that this week by including an ORDER BY clause in a subquery that feeds an INSERT statement. It raises an ORA-00907 exception, like:

ORA-00907: missing right parenthesis

You can’t include a subquery with an ORDER BY clause because it generates an error. The reason is simple. A subquery can’t perform a sort operation inside a subquery. Here’s a quick demonstration:

DROP TABLE destination;
CREATE TABLE destination
( destination_id    NUMBER
, destination_name  VARCHAR2(20));
 
INSERT INTO destination
(
  SELECT   1,'Sample1' FROM dual
  UNION ALL
  SELECT   2,'Sample2' FROM dual
  ORDER BY 1 DESC
);

If you remove the ORDER BY clause, the statement works without a problem. For example, here’s the working version:

INSERT INTO destination
(
  SELECT   1,'Sample1' FROM dual
  UNION ALL
  SELECT   2,'Sample2' FROM dual
);

Alternatively, you can include an ORDER BY clause when you remove the parentheses from around the subquery. This is an example:

INSERT INTO destination
  SELECT   1,'Sample1' FROM dual
  UNION ALL
  SELECT   2,'Sample2' FROM dual
  ORDER BY 1 DESC;

I hope this helps anybody who runs into the problem.

Written by maclochlainn

June 14th, 2014 at 10:40 pm