Oracle date changed user changed columns and batch performance

Most core application tables benefit from columns like these: ALTER TABLE mytable ADD ( date_created DATE DEFAULT SYSDATE , user_created_by VARCHAR2(30) DEFAULT USER , date_changed DATE , user_changed_by VARCHAR2(30) ) ; The default values deal with inserts, for updates a trigger is needed: CREATE OR REPLACE TRIGGER tu_mytable BEFORE UPDATE ON mytable FOR EACH ROW […]

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October 16, 2015

execute immediate quote escape oracle pl/sql

To run this via execute immediate: CREATE TABLE t2 AS SELECT * FROM t1 WHERE col1 = ‘1’ ; Either use new style quote format: EXECUTE IMMEDIATE q'[CREATE TABLE t2 AS SELECT * FROM t1 WHERE col1 = ‘1’]’ ; Or older style still works also: EXECUTE IMMEDIATE ‘CREATE TABLE t2 AS SELECT * FROM […]

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April 25, 2015

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Partition an existing oracle table example

I used this SQL to convert an existing non-partitioned table to be partitioned. Table was mostly queried on snapshot_id=’Current’, which had the most up to date data, but had much more historic data that was rarely queried against, all flagged with snapshot_id = ‘YYYYMMDD’ format. — 1) Create an empty table with one partition CREATE […]

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April 25, 2015

SQL to display date duration as number of years and months

Convert date duration (here customer age at time of first application) in years and months, e.g. ‘3408’ for 34 years and 8 months old: WITH customers AS ( SELECT SYSDATE AS appl_date , TO_DATE ( ’01-AUG-1980′ , ‘DD-MON-YYYY’ ) AS date_of_birth FROM DUAL ) SELECT TO_CHAR ( GREATEST ( 0 , LEAST ( 99 , […]

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April 24, 2015

Rebuild table indexes lobs in oracle

Rebuilds are beneficial in some rare circumstances such as after a mass delete operation. The below method is safer and faster than export/import. Example table: CREATE TABLE tab1 ( col1 VARCHAR2(1) , col2 CLOB ) TABLESPACE ts1 ; CREATE INDEX tab1i ON tab1 ( col1 ) TABLESPACE ts1 ; List objects and tablespaces: SELECT tablespace_name […]

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January 20, 2015

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Oracle data transform using analytic lag row_number case

So I needed to transform this source data: Into this output format: Seems simple, but required a combination of CASE, LAG, and ROW_NUMBER – as Tom Kyte steps through in detail in this article from 2004. Here is the solution: SELECT q5.event_category , q5.num , MIN ( q5.week ) AS start_week , MAX ( q5.week […]

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December 17, 2014

Run Windows interactive scheduled task even if user not logged in

http://superuser.com/questions/616206/run-interactive-task-even-if-user-is-not-logged-on-windows?rq=1 Problem arises when a windows scheduled task needs to fire up a GUI – if there is no session logged in then it fails to run because has nowhere to display the GUI. Caveat: I haven’t tried this solution myself yet, don’t know if there are any unpleasant side effects from it or not.

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November 24, 2014

Data from MySQL to Oracle with dg4odbc database link or mysqldump

To transfer data from MySQL into Oracle 1) Best method is to use a database link. That way the MySQL table is available in the Oracle database for use in queries, joins, DML, PL/SQL. Simple guides on how to do to that are: Shishir Tekade http://www.shishirtekade.com/2014/01/connect-oracle-to-mysql-server-through.html Pythian http://www.pythian.com/blog/how-to-access-mysql-from-oracle-with-odbc-and-sql/ My Oracle Support 1320645.1 ‘Detailed Overview of […]

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November 18, 2014

Analytics row_number to identify first parent row in oracle pl/sql cursor loop

Let’s say you have 10m parent rows and 11m child rows and need to process them row-at-a-time in pl/sql. Two methods of doing that are below. The second method will fire the combined select just the once, picking up all 11m rows in one go. The first method will fire the child select 10m times […]

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October 22, 2014

oracle substrb function to chop a string down to its first 4000 bytes

The substrb 1 , 4000 function will chop a string down to its first 4000 bytes, e.g.: SELECT SUBSTR(‘1€3’,2,1) , SUBSTRB(‘1€3’,1,3) , LENGTH(‘1€3’) , LENGTHB(‘1€3′) FROM dual ; Needed if using the (non default) option of ‘char’ in column lengths: CREATE TABLE mytable ( col1 VARCHAR2(4000 CHAR) ) ; You can change the default setting […]

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August 25, 2014