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Condition expression

Last updated: 2024-08-22 16:23:50

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CASE

The database supports CASE expressions, similar to the IF/ELSE feature in other languages.
Example:
SELECT a,
       CASE WHEN a=1 THEN 'one'
            WHEN a=2 THEN 'two'
            ELSE 'other'
       END
    FROM test;

COALESCE

COALESCE returns the first non-NULL value among its parameters. If all parameters are NULL, it returns NULL.
SELECT COALESCE(null,1,2,null) ;       

 coalesce 

----------

       1

NULLIF

NULLIF(value1, value2) returns: if value1 and value2 are equal, it returns NULL. Otherwise, it returns value1.

GREATEST and LEAST

These two functions return the largest or smallest value from a list of values, respectively. When all parameters are NULL, it returns NULL.
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