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Simple CASE Expression


CASE expr
WHEN when_expr THEN result_expr
{WHEN when_expr THEN result_expr}
[ELSE else_expr]

Simple CASE evaluates expr, and then, in the order specified, evaluates expr = when_expr for each WHEN clause. Simple CASE returns the result_expr of the first WHEN clause that evaluates to TRUE. If no match is found, CASE returns the else_expr if an ELSE clause is specified, or a NULL value if no ELSE clause is specified.


This example uses a CASE expression to alter the display of book categories to make them more understandable.

SELECT Category = 
CASE type
WHEN 'popular_comp' THEN 'Popular Computing'
WHEN 'mod_cook' THEN 'Modern Cooking'
WHEN 'business' THEN 'Business'
WHEN 'psychology' THEN 'Psychology'
WHEN 'trad_cook' THEN 'Traditional Cooking'
ELSE 'Not yet categorized'
price AS Price
FROM titles
Equivalents in other databases 
TABLE 89. Equivalents in other databases
Simple CASE expression
DECODE expression

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