这个MySQL脚本有什么不对吗？

Question

SELECT @cnt := COUNT(table_name) 
  FROM information_schema.tables 
 WHERE table_schema = 'TAA' 
   and table_name = 'Clients';

IF (@cnt > 0) THEN
  INSERT INTO `ClientsBAK` SELECT * FROM `Clients`;
END IF;

我在IF(@cnt > 1) THEN错误1064

时收到语法错误

Answer 1

AFAIK，你只能在例程（函数，触发器，存储过程）中使用IF。

Answer 2

创建存储过程：

DELIMITER //
CREATE PROCEDURE BackupClients()
BEGIN

    SELECT @cnt := COUNT(table_name)
    FROM information_schema.tables
    WHERE table_schema = 'TAA'
    AND table_name = 'Clients';

    IF @cnt > 0 THEN
        INSERT INTO `ClientsBAK` SELECT * FROM `Clients`;
    END IF;

END //
DELIMITER ;

CALL BackupClients();

我认为你也想要IF @cnt > 0而不是IF @cnt > 1，所以我为你改变了。