Dev Corner

Oracle PL/SQL Collections and Associative Arrays

baobab — Thu, 10 Dec 2009 13:56:07 +0000

Associative Arrays

DECLARE
  TYPE population_type IS TABLE OF NUMBER INDEX BY VARCHAR2(64);
  country_population population_type;
  continent_population population_type;
  howmany NUMBER;
  which VARCHAR2(64);
 
BEGIN
  country_population('Greenland') := 100000;
  country_population('Iceland') := 750000;
  howmany := country_population('Greenland');
 
  continent_population('Australia') := 30000000;
  continent_population('Antarctica') := 1000; -- Creates new entry
  continent_population('Antarctica') := 1001; -- Replaces previous value
  dbms_output.put_line('Count: ' || continent_population.count);
 
  which := continent_population.FIRST; -- Returns 'Antarctica'
 
-- as that comes first alphabetically.
  which := continent_population.LAST; -- Returns 'Australia'
  howmany := continent_population(continent_population.LAST);
-- Returns the value corresponding to the last key, in this
-- case the population of Australia.
 
  -- Traverse Continents Associative Array
  dbms_output.put_line('Elements in continent_population: ' || continent_population.count);
  which := continent_population.FIRST;
  WHILE which IS NOT NULL LOOP
    dbms_output.put_line(which || ': ' || continent_population(which));
    which := continent_population.NEXT(which);
  END LOOP;
  -- Outputs:
  --   Count: 2
  --   Elements in continent_population: 2
  --   Antarctica: 1001
  --   Australia: 30000000
 
END;

Extend Oracle PL/SQL Collection

DECLARE
  TYPE CourseList IS TABLE OF VARCHAR2(10);
  courses CourseList := CourseList();
BEGIN
  dbms_output.put_line('Initial count= ' || courses.count ||
                       ', first= ' || courses.first ||
                       ', last= ' || courses.last ||
                       '');
  courses.extend(5);
  dbms_output.put_line('After extend(5) count= ' || courses.count ||
                       ', first= ' || courses.first ||
                       ', last= ' || courses.last ||
                       '');
  dbms_output.put_line('After extend(5) count: ' || courses.count);
 
END;

Initial count= 0, first= , last=
After extend(5) count= 5, first= 1, last= 5
After extend(5) count: 5

Oracle Database Multitable INSERT SQL

baobab — Thu, 10 Dec 2009 09:30:56 +0000

Multitable INSERT SQL can insert simultaneously into more than one tables. You can also specify optional conditions which determine which values are inserted into which tables.

SELECT * FROM sales_input_table;
 
PRODUCT_ID CUSTOMER_ID WEEKLY_ST  SALES_SUN  SALES_MON  SALES_TUE  SALES_WED SALES_THU  SALES_FRI  SALES_SAT
---------- ----------- --------- ---------- ---------- ---------- -------------------- ---------- ----------
       111         222 01-OCT-00        100        200        300        400       500        600        700
       222         333 08-OCT-00        200        300        400        500       600        700        800
       333         444 15-OCT-00        300        400        500        600       700        800        900

The multitable insert statement looks like this:

INSERT ALL
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date, sales_sun)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+1, sales_mon)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+2, sales_tue)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+3, sales_wed)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+4, sales_thu)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+5, sales_fri)
      INTO sales (prod_id, cust_id, time_id, amount)
      VALUES (product_id, customer_id, weekly_start_date+6, sales_sat)
   SELECT product_id, customer_id, weekly_start_date, sales_sun,
      sales_mon, sales_tue, sales_wed, sales_thu, sales_fri, sales_sat
      FROM sales_input_table;

Assuming these are the only rows in the sales table, the contents now look like this:

SELECT * FROM sales
   ORDER BY prod_id, cust_id, time_id;
 
   PROD_ID    CUST_ID TIME_ID   C   PROMO_ID QUANTITY_SOLD     AMOUNT       COST
---------- ---------- --------- - ---------- ------------- ---------- ----------
       111        222 01-OCT-00                                   100
       111        222 02-OCT-00                                   200
       111        222 03-OCT-00                                   300
       111        222 04-OCT-00                                   400
       111        222 05-OCT-00                                   500
       111        222 06-OCT-00                                   600
       111        222 07-OCT-00                                   700
       222        333 08-OCT-00                                   200
       222        333 09-OCT-00                                   300
       222        333 10-OCT-00                                   400
       222        333 11-OCT-00                                   500
       222        333 12-OCT-00                                   600
       222        333 13-OCT-00                                   700
       222        333 14-OCT-00                                   800
       333        444 15-OCT-00                                   300
       333        444 16-OCT-00                                   400
       333        444 17-OCT-00                                   500
       333        444 18-OCT-00                                   600
       333        444 19-OCT-00                                   700
       333        444 20-OCT-00                                   800
       333        444 21-OCT-00                                   900

The next examples insert into multiple tables. Suppose you want to provide to sales representatives some information on orders of various sizes. The following example creates tables for small, medium, large, and special orders and populates those tables with data from the sample table oe.orders:

CREATE TABLE small_orders
   (order_id       NUMBER(12)   NOT NULL,
    customer_id    NUMBER(6)    NOT NULL,
    order_total    NUMBER(8,2),
    sales_rep_id   NUMBER(6)
   );

CREATE TABLE medium_orders AS SELECT * FROM small_orders;

CREATE TABLE large_orders AS SELECT * FROM small_orders;

CREATE TABLE special_orders
   (order_id       NUMBER(12)    NOT NULL,
    customer_id    NUMBER(6)     NOT NULL,
    order_total    NUMBER(8,2),
    sales_rep_id   NUMBER(6),
    credit_limit   NUMBER(9,2),
    cust_email     VARCHAR2(30)
   );

The first multitable insert populates only the tables for small, medium, and large orders:

INSERT ALL
   WHEN order_total < 1000000 THEN
      INTO small_orders
   WHEN order_total > 1000000 AND order_total < 2000000 THEN
      INTO medium_orders
   WHEN order_total > 2000000 THEN
      INTO large_orders
   SELECT order_id, order_total, sales_rep_id, customer_id
      FROM orders;

You can accomplish the same thing using the ELSE clause in place of the insert into the large_orders table:

INSERT ALL
   WHEN order_total < 100000 THEN
      INTO small_orders
   WHEN order_total > 100000 AND order_total < 200000 THEN
      INTO medium_orders
   ELSE
      INTO large_orders
   SELECT order_id, order_total, sales_rep_id, customer_id
      FROM orders;
<pre>
 
The next example inserts INTO the small, medium, AND large TABLES, AS IN the preceding example, AND also puts orders greater than 2,900,000 INTO the special_orders TABLE. This TABLE also shows how TO USE COLUMN aliases TO simplify the statement:
 
<pre lang="sql">
INSERT ALL
   WHEN ottl < 100000 THEN
      INTO small_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 100000 AND ottl < 200000 THEN
      INTO medium_orders 
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 200000 THEN
      INTO large_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 290000 THEN
      INTO special_orders
   SELECT o.order_id oid, o.customer_id cid, o.order_total ottl,
      o.sales_rep_id sid, c.credit_limit cl, c.cust_email cem
      FROM orders o, customers c
      WHERE o.customer_id = c.customer_id;

Finally, the next example uses the FIRST clause to put orders greater than 2,900,000 into the special_orders table and exclude those orders from the large_orders table:

INSERT FIRST
   WHEN ottl < 100000 THEN
      INTO small_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 100000 AND ottl < 200000 THEN
      INTO medium_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 290000 THEN
      INTO special_orders
   WHEN ottl > 200000 THEN
      INTO large_orders
         VALUES(oid, ottl, sid, cid)
   SELECT o.order_id oid, o.customer_id cid, o.order_total ottl,
      o.sales_rep_id sid, c.credit_limit cl, c.cust_email cem
      FROM orders o, customers c
      WHERE o.customer_id = c.customer_id;

Oracle Multi-table Insert Syntax


INSERT [hint]
   {
      ALL insert_into_clause [values_clause] [error_logging_clause]
            [insert_into_clause [values_clause] [error_logging_clause]]...
      |
      conditional_insert_clause
   }

conditional_insert_clause ::=
   [ALL | FIRST]
   WHEN condition
      THEN
	     insert_into_clause
            [ values_clause ]
            [ error_logging_clause ]
         [ insert_into_clause
            [ values_clause ]
            [ error_logging_clause ]
         ]...
   [ WHEN condition
      THEN
	     insert_into_clause
            [ values_clause ]
            [ error_logging_clause ]
         [ insert_into_clause
            [ values_clause ]
            [ error_logging_clause ]
         ]...
   ]...

   [ ELSE insert_into_clause
      [ values_clause ]
         [ error_logging_clause ]
      [ insert_into_clause
         [ values_clause ]
         [ error_logging_clause ]
      ]...
   ]

insert_into_clause :=
   INTO dml_table_expression_clause [ t_alias ]
      [ (column [, column ]...) ]

values_clause :=
   VALUES ({ expr | DEFAULT }
      [, { expr | DEFAULT } ]...
   )

Find SQL Executed by a Session – Oracle

baobab — Tue, 08 Dec 2009 13:32:07 +0000

The following SQL shows the SQL text for the SQL being executed by a session.

SELECT s.sid,
       q.sql_text
  FROM v$sqltext q
       JOIN v$session s ON q.address = s.sql_address
 WHERE s.sid = &sid
 ORDER BY piece;

Show the Longest 10 Active User Sessions

baobab — Mon, 07 Dec 2009 13:34:54 +0000

The following SQL can be used by Oracle Database Administrator (DBA) to retrieve information about the currently active sessions with longest execution. The SQL statement is designed to run with SQL*Plus.

To show a list with top current sessions with longest acivity execute in SQL*Plus:

/*
  longest10active.sqlplus.sql
  shows the top 10 active sessions with longest execution activity
  execute in SQL*Plus
*/
col osuser format a10 trunc
col LastCallET format 99,999
col sid format 9999
col spid formar 999999
col username format a10 trunc
col uprogram format a25 trunc
col machine format a10 trunc
SET linesize 132
SET verify off
 
SELECT * FROM (
   SELECT TO_CHAR(s.logon_time, 'mm/dd hh:mi:ssAM') loggedon,
          s.sid, s.STATUS,
          floor(last_call_et/60) "LastCallET",
          s.username, s.osuser,
          p.spid, s.module || ' - ' || s.program uprogram,
          s.machine, s.sql_hash_value
     FROM v$session s, v$process p
    WHERE p.addr = s.paddr
          AND s.type = 'USER'
          AND module IS NOT NULL
          AND s.STATUS = 'ACTIVE'
    ORDER BY 4 DESC)
WHERE ROWNUM < 11;

If you want the execute the statement in different tool, you can remove the formatting clauses:

/*
  longest10active.sql
  shows the top 10 active sessions with longest execution activity
*/
SELECT * FROM (
   SELECT TO_CHAR(s.logon_time, 'mm/dd hh:mi:ssAM') loggedon,
          s.sid, s.STATUS,
          floor(last_call_et/60) "LastCallET",
          s.username, s.osuser,
          p.spid, s.module || ' - ' || s.program uprogram,
          s.machine, s.sql_hash_value
     FROM v$session s, v$process p
    WHERE p.addr = s.paddr
          AND s.type = 'USER'
          AND module IS NOT NULL
          AND s.STATUS = 'ACTIVE'
    ORDER BY 4 DESC)
WHERE ROWNUM < 11;

References

Oracle Applications World: Show the top 10 longest-active user sessions

Select and Return Top N Rows from Oracle Database

baobab — Mon, 07 Dec 2009 11:55:11 +0000

We often need to limit the number of rows returned by a select statement. Some database servers provide extensions to the select statement. For example, MySql database sever provides LIMIT directive. In Oracle Database each result set has defined a ROWNUM pseudocolumn and ORDER BY clause interact.

Let’s create a test table with some data loaded in reverse order.

CREATE TABLE numbers (
  id  NUMBER
);
 
INSERT INTO numbers (id) VALUES (10);
INSERT INTO numbers (id) VALUES (9);
INSERT INTO numbers (id) VALUES (8);
INSERT INTO numbers (id) VALUES (7);
INSERT INTO numbers (id) VALUES (6);
INSERT INTO numbers (id) VALUES (5);
INSERT INTO numbers (id) VALUES (4);
INSERT INTO numbers (id) VALUES (3);
INSERT INTO numbers (id) VALUES (2);
INSERT INTO numbers (id) VALUES (1);
COMMIT;

We want the first 3 rows from the SELECT result set:

SELECT * FROM numbers WHERE ROWNUM <= 3;
 
     ID
-------
     10
      9
      8

We want to retrieve only the records with the smallest 3 IDs.

SELECT * FROM numbers 
 WHERE ROWNUM <= 3
 ORDER BY id;
 
     ID
-------
      8
      9
     10

The result is not what we expected. The reason is that Oracle first fetches the records based on selection predicate and than sort the resulting rows. In our case, Oracle first filters the first three rows with IDs 10, 9 and 8 and than sorts them.

To achieve the desired result we need first to sort the records and then select the first 3 rows. For this we can use nested selects:

SELECT * FROM (SELECT * FROM numbers
                ORDER BY id)
 WHERE ROWNUM <= 3;
 
     ID
-------
      1
      2
      3

The Oracle first executes the innermost sub-select. Thus Oracle fetches all the rows and orders them. Than Oracle Database executes the outer select which filters only the first 3 rows.

We can use the same technique to retrieve the top 2 rows, i.e. the 2 rows with the biggest ID:

SELECT * FROM (SELECT * FROM numbers
                ORDER BY id DESC)
 WHERE ROWNUM <= 2;
 
     ID
-------
     10
      9

Select queries that return the first N rows from an ordered result set are also known as Top-N queries.

References

Top-N Queries [http://www.oracle-base.com/articles/misc/TopNQueries.php]
Top N Oracle Database SELECT Rows

Split long command on Windows / Linux into multiple lines – multiline command

baobab — Sun, 06 Dec 2009 21:45:02 +0000

You can easily split long command line into multiple lines.

How to split long commands on multiple lines on Linux

Add a backslash character at the end of line to tell the Linux shell that the next line continues the current line.

   ls \
     -a

How to split long commands on multiple lines on Windows

Add a ^ character at the end of line to tell the Windows Command Interpreter that the next line continues the current line.

  dir ^
    -s

Discussion
In the Windows Command Prompt the ^ is used to escape the next character on the command line. (Like \ is used in strings.) Characters that need to be used in the command line as they are should have a ^ prefixed to them, hence that’s why it works for the newline.

For reference the characters that need escaping (if specified as command arguments and not within quotes) are: &|()

WordPress Plugin: bb:Usage Stats

baobab — Sat, 05 Dec 2009 20:32:06 +0000

bb: Usage Stats collects information about page, post, category and homepage views for your WordPress blog. Builds daily and monthly usage statistics.

To preserve database storage space, old usage information is purged from the database.

Graphical display of the daily usage statistics. Additional bar-graph chart that displays top 15 pages, posts and categories.

Adds dasboard widget that displays daily usage statistics chart and top 15 pages, post and categories.

You can download the current version from WordPress.org.

Screenshots

Sample daily usage chart.

Sample “Top 15″ bar-graph chart.

Thumbnail view for the full statistics display.

Revision History

= 1.0 =

Fix: activation hook doesn’t create track table.

= 1.0 =

Dashboard widget with summary chart and Top 15 bar-graph chart
Display Top 15 Bar-graph chart
Display summary statistics graph chart
Administrative page
Track home page views
Track category views
Track post views
Track page views
Initial plugin release

WordPress Plugin bb:Text Rotator Widget

baobab — Sat, 05 Dec 2009 18:35:38 +0000

The bb:Text Rotator WordPress plugin contains bb:Text Rotator Widget.

As any WordPress widget, you can add the bb:Text Rotator Widget to any sidebar using the WordPress administrative interface (Appearance – Widgets menu). From the Widget administration form you can define text snippets. You can specify as many text snippets as you like.

When WordPress builds the output HTML, the widget randomly selects a snippet and inserts it in place of the widget.

Any widget have a priority. The higher is the priority of the snippet, the higher is the chance that it will be selected for display.

Current Stable Version: [TODO] [Download]

Previous Versions: [TODO]

Data Expressions or Backus-Naur Form (BNF)

baobab — Wed, 02 Dec 2009 13:20:59 +0000

Data expressions can be used to describe structure of data.

Example: Data Expression with plus as concatenator

booking request = guest data + period + room type

guest data = guest name + address + paymethod
           + [passport number]

passport number = letter + {digit}*8

room state = {free | booked | occupied | repair}

account data = transfer + {account record}* + done

Example: Data Expression with implicit concatenation

guestData = guestName, address, paymethod
         [, passportNumber]

if_statement = 'if' condition 'Then' statement
              ['Else:' statement 'End If']

+ Shows the sequence of data. What comes after what.
[ ] Shows that something is optional.
[optional-expression]
{ }* Shows that something is repeated a number of times.
{expression}*
{expression}*8
{expression}*(0:8)
{expression}*(4:*)
{ | | } Shows a choice between several possibilities.
B = C Shows that the composite data structure B is composed as shown by C.
‘free’ Shows a literal value.
If we want a comma to separate the data parts, we
show a comma in the formula.

Software Requirements – Styles and Techniques

WordPress Tutorial: Create Shortcode

admin — Thu, 26 Nov 2009 18:32:21 +0000

Shortcodes are very effective way to include dynamic content into your posting. This tutorial will guide you through the process of creating your own shortcode. Just in few easy steps.

In just few minutes you will create a shortcode that includes the post publication date. When you include [post-date] in your post, WordPress will replace it automatically with the post date.

1. Create a new post

Let’s start with creating a post to play with. Publish the post. Here is the post I created.

For this tutorial I am using the default WordPress theme. At the end of the post I have inserted [post-date] shortcode.
Because the shortcode is not implemented yet, WordPress displays it literally without replacing it.

2. Create a new plugin.

Plugins are placed under WordPress plugins directory. It is good practice to place each plugin into a separate directory.

Create a new directory named post-date under WordPress plugins directory (wp-content/plugins).

Using a text editor, create a text file named post-date.php. You can use any file name that you like, but for this tutorial we will use the post-date.php.

Now you have an empty text file: wp-content/plugins/post-date/post-date.php. This file will contain the code for the shortcode handler.

3. Define the plugin

To identify plugins WordPress uses comments that conform to special format. Enter the following plugin definition in the post-date.php file.


/*
Plugin Name: Post-date short code
Plugin URI: http://devcorner.georgievi.net
Description: This plugin defined a 'post-date' shortcode handler.
Author: Ivan Georgiev
Version: 1.5.1
Author URI: http://devcorner.georgievi.net/
*/
?>

Now you have a plugin defined. You are able to see it under Plugins list in WordPress administrator.

4. Add shortcode handler code

We will create a PHP function that will be invoked when WordPress needs to replace a post-date shortcode.


/*
Plugin Name: Post-date short code
Plugin URI: http://devcorner.georgievi.net
Description: This plugin defined a 'post-date' shortcode handler.
Author: Ivan Georgiev
Version: 1.5.1
Author URI: http://devcorner.georgievi.net/
*/
 
function post_date_handler($atts) {
	global $post;
	return mysql2date('M jS, Y', $post->post_date);
}
 
add_shortcode('post-date', 'post_date_handler');
 
?>

The add_shortcode function instructs WordPress to invoke the post_date_handler function when it needs to replace a post-date shortcode.

The post_date_handler function returns the formatted date for the current post.

Now you have everyting ready. If you try to view the post you created at the beginning of this tutorial, you will see no change. Why?

One small thing left. You need to activate the newly created plugin.

5. Activate the plugin

Go to the Plugins section in WordPress administrative section. In the plugin list find the ‘Post-date shortcode’ plugin and click the ‘Activate’ link to activate it.

Open the post and voila! You see that the shortcode text is replaced by the post date.

If you want to include ‘[post-date]‘ as a text, you need to use double brackets. You enter ‘[[post-date]]’ to get ‘[post-date]‘.

This tutorial covers only WordPress shortcode basics. For more detailed description see WordPress shortcode API.