Criteria for judging in MySQL

• If/case when to judge

Select Case 1 if 1 then "one" while 2 then "one" and "more" END; "One" Select Case when    1>0 and "true" ELSE "false" END; "true" Select Case    BINARY "B" when "a" N 1 when the "B" then 2 END; and NULL    (1) Case VALUE when [compare-value] then result [when [compare-value] then result ...] [ELSE result] END//This I have not thought of how to use, know can message exchange,    (2) case when [CONDITION] then result [when [CONDITION] then result ...] [ELSE result] END//This interview was asked by people, can be used as a condition to judge

• ISNULL judgment

Usage of ISNULL (expr):    If expr is null, then the return value of ISNULL () is 1, otherwise the return value is 0.    ifnull (EXPR1,EXPR2) Usage:    If EXPR1 is   not   NULL, the   return value of Ifnull ()   is   expr1;    Otherwise its return value is   expr2. The return value of Ifnull () is either a number or a string, depending on the context in which it is used.

Criteria for judging in MySQL