Logical functions
CASE
Syntax:CASE expression WHEN value_1 THEN result_1 [ WHEN value_2 THEN result_2 ... ] ELSE default_result END
orCASE( expression, value_1, result_1, [ value_2, result_2, ... ] default_result )
Compares expression
to value_1
, value_2
, ... consecutively and returns the corresponding result for the first match. If no match is found, it returns default_result
.
IF
Syntax:IF condition_1 THEN result_1 [ ELSEIF condition_2 THEN result_2 ... ] ELSE default_result END
orIF( condition_1, result_1, [ condition_2, result_2, ... ] default_result )
Checks conditional expressions condition_1
, result_1
, ... and returns the matching result for the first condition found to be TRUE
. IF all conditional expressions are FALSE
, it returns default_result
. The expressions to be checked are set using logical operators.
IFNULL
Syntax:IFNULL( check_value, alt_value )
Returns check_value
if it's not NULL
. Otherwise returns alt_value
.
ISNULL
Syntax:ISNULL( expression )
orexpression IS [ NOT ] NULL
Returns TRUE
if expression
is NULL
, otherwise returns FALSE
.
expression IS NOT NULL
returns the opposite result.
ZN
Syntax:ZN( expression )
Returns expression
if it's not NULL
. Otherwise returns 0.