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Don Burleson Blog 









Oracle Functions

Oracle Database Tips by Donald Burleson

Oracle SQL provides functions (built-in) and Oracle allows you to define custom functions using PL/SQL.

By creating your own Oracle functions you can extend your dialect of SQL and add your own special data transformations.  Common language functions such as substring (substr) and data type transformation functions (to_char, to_date) are built in.

You can also create function-based indexes, a great SQL tuning tool.  Any Oracle function that can be expressed in SQL can also be used in an index.

Oracle functions can be placed within other Oracle functions, and here is an example of deeply nested Oracle functions in SQL:

         DECODE (
            SUBSTRB (
               USERENV (
                  'CLIENT_INFO'),1,1),' ', NULL,
               SUBSTRB (
            USERENV ('CLIENT_INFO'),1,10)
from mytab;


Here are my notes on common Oracle functions in SQL:

If you like Oracle tuning, you may enjoy my new book "Oracle Tuning: The Definitive Reference", over 900 pages of BC's favorite tuning tips & scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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