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  • Control Flow Functions

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    Hello friends, Today I am here to explain the control flow function of mysql. Some times you want to get the result with respect to some conditions then you can use these functions.

    Here are 4 type of control flow function which are following- Flow Control Operators

    Name                  Description
    
    CASE                  Case operator
    IF()                  If/else construct
    IFNULL()              Null if/else construct
    NULLIF()              Return NULL if expr1 = expr2
    

    Here are some examples which will explain you these functions-

    CASE value WHEN [compare_value] THEN result [WHEN [compare_value] THEN result ...] [ELSE result] END CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...] [ELSE result] END

    mysql> SELECT CASE 1 WHEN 1 THEN 'one'
        ->     WHEN 2 THEN 'two' ELSE 'more' END;
            -> 'one'
    mysql> SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;
            -> 'true'
    mysql> SELECT CASE BINARY 'B'
        ->     WHEN 'a' THEN 1 WHEN 'b' THEN 2 END;
            -> NULL 
    

    IF(expr1,expr2,expr3)

    mysql> SELECT IF(1>2,2,3);
            -> 3
    mysql> SELECT IF(1<2,'yes','no');
            -> 'yes'
    mysql> SELECT IF(STRCMP('test','test1'),'no','yes');
            -> 'no'NULLIF(expr1,expr2)
    

    IFNULL(expr1,expr2)

    mysql> SELECT IFNULL(1,0);
            -> 1
    mysql> SELECT IFNULL(NULL,10);
            -> 10
    mysql> SELECT IFNULL(1/0,10);
            -> 10
    mysql> SELECT IFNULL(1/0,'yes');
            -> 'yes'
    

    NULLIF(expr1,expr2)

    mysql> SELECT NULLIF(1,1);
            -> NULL
    mysql> SELECT NULLIF(1,2);
            -> 1
    

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