CASE allows you to return different values under different conditions.

If there no conditions match (and there is not ELSE) then NULL is returned.

 CASE WHEN condition1 THEN value1 
 WHEN condition2 THEN value2 
 ELSE def_value 
 END 

SELECTname,population
,CASEWHENpopulation<1000000
THEN'small'
WHENpopulation<10000000
THEN'medium'
ELSE'large'
END
FROMbbc

See also

• NVL function