mysql - 不能在带有 PRINT 语句的 MySQL 中使用 IF/ELSE

Question

当 MySQL 中的条件为真时，我试图打印一些东西。这是我的代码:

BEGIN

UPDATE president
INNER JOIN election ON president.pres_name = election.candidate
SET yrs_serv = yrs_serv + 4
WHERE election.winner_loser_indic = 'W'
AND election.election_year = (SELECT MAX(election_year) FROM election)

BEGIN
IF (yrs_serv > 4) THEN BEGIN PRINT "warning"
END
END

END

当我运行它时，我得到了这个错误。

MySQL: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'BEGIN IF (yrs_serv > 4) THEN BEGIN PRINT "warning" END END END' at line 7

这是在一个过程中。我想不通。如果我不尝试使用 IF 语句，代码就可以工作。

Answer 1

首先，您在 update 末尾缺少 ;，然后 IF 不需要 Begin。然后IF的结束由END IF;完成，只需要一个Begin .... End试试下面的代码

BEGIN

UPDATE president
INNER JOIN election ON president.pres_name = election.candidate
SET yrs_serv = yrs_serv + 4
WHERE election.winner_loser_indic = 'W'
AND election.election_year = (SELECT MAX(election_year) FROM election);


IF (yrs_serv > 4) THEN 
 Select "warning"; // PRINT "warning" can be achived by Select
END IF;

END;