Mysql 流程控制

Mysql 流程控制语句

IF语句

IF search_condition THENstatement_list
[ELSEIF search_condition THEN ``statement_list] ...
[ELSEstatement_list]
END IF“`

if-then-elseif-then-else-end if; 这里就不啰嗦了！

CASE语句

CASE case_value
WHEN when_value THENstatement_list
[WHEN when_value THEN statement_list] …
[ELSE statement_list]
END CASE；
使用场景：比较对象case_value值与分支的值相同
Or:

CASE
WHEN search_condition THENstatement_list
[WHEN search_condition THEN statement_list] …
[ELSE statement_list]
END CASE

使用场景：满足when 条件的分支表达式不确定

LOOP循环语句

[begin_label:] LOOP
statement_list
END LOOP [end_label]

loop -leave-end loop

REPEAT循环语句

[begin_label:] REPEAT
statement_list
UNTIL search_condition
END REPEAT [end_label]

WHILE语句

[begin_label:] WHILE search_condition DO
statement_list
END WHILE [end_label]

– 个人建议使用常见的

代码案例

DROP PROCEDURE IF EXISTS procedure_function;CREATE PROCEDURE procedure_function (in inputparam VARCHAR(64))BEGIN    DECLARE tableName VARCHAR(64) DEFAULT '';    DECLARE tableId BIGINT(64) DEFAULT 0;    DECLARE num BIGINT(64) UNSIGNED   DEFAULT 5;  -- IF  IF num > 1 THEN     SELECT * FROM t_bversion ;    SET num = num - 3;  ELSE    SELECT * FROM t_iteration;  END IF;  -- CASE  CASE  num     WHEN 1 THEN             SELECT CONCAT('NUM1=',num);    WHEN 3 THEN             SELECT CONCAT('NUM3=',num);    ELSE            SELECT CONCAT('NUM=',num);  END CASE;  CASE      WHEN num > 0 AND num < 2 THEN         SELECT CONCAT('表达式不确定');                SELECT CONCAT('列表不确定');    WHEN num = 0 OR num = 2 THEN                SELECT CONCAT('NUM=',num);    ELSE        SELECT CONCAT('other=',num);  END CASE;  -- LOOP     lable:LOOP     SET num = num -1;        SELECT CONCAT('Loop循环',num);    IF num != 0 THEN             ITERATE lable; -- 继续循环    END IF;        LEAVE lable;     -- 跳出循环    END LOOP lable;      -- REPEAT        SET num = 3;        REPEAT             SELECT CONCAT('REPEAT循环',num);             SET num = num -1;        UNTIL num = 0     -- 为真跳出        END REPEAT;         -- WHILE        SET num = 5;        WHILE num < 0 DO -- 为真循环             SELECT CONCAT('while循环',num);             SET num = num -1;        END WHILE;END;CALL procedure_function(NULL);