MySQL DECLARE 中的 SELECT INTO 变量导致语法错误?

2021-12-19 00:00:00 select mysql mysql-workbench declare

我想将单个值 SELECT 到一个变量中.我试图遵循:

I´d like to SELECT a single value into a variable. I´d tried to following:

DECLARE myvar INT(4);

-- 立即返回一些语法错误.

-- immediately returns some syntax error.

SELECT myvalue 
  FROM mytable 
 WHERE anothervalue = 1;

-- 返回一个整数

SELECT myvalue 
  INTO myvar 
  FROM mytable 
 WHERE anothervalue = 1;

-- 不行，也试过@myvar

-- does not work, also tried @myvar

是否可以在存储过程或函数之外使用 DECLARE?

Is possible to use DECLARE outside of stored procedures or functions?

也许我只是不明白用户变量的概念......我只是试过:

Maybe I just dont get the concept of user variables... I just tried:

SELECT myvalue INTO @var FROM `mytable` WHERE uid = 1;
SELECT @var;

...就像它应该的那样工作.但是如果我一次运行每个查询，我只会得到@var NULL.

...which worked just like it´s supposed to. But if I run each query at a time i just get @var NULL.

推荐答案

最后一个存储过程解决了我的问题.

In the end a stored procedure was the solution for my problem.

这里有什么帮助:

DELIMITER //

CREATE PROCEDURE test ()
BEGIN
  DECLARE myvar DOUBLE;
  SELECT somevalue INTO myvar FROM mytable WHERE uid = 1;

  SELECT myvar;
END//

DELIMITER ;

call test();

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