MySQL DECLARE中的​​SELECT INTO变量会导致语法错误? [英] SELECT INTO Variable in MySQL DECLARE causes syntax error?

问题描述

我想将一个值选择为一个变量.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;

-不起作用，也尝试了@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?

也许我只是不了解用户变量的概念...我只是试过了:

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

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

...它的工作原理与预期的一样.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，存储过程是解决我的问题的方法.这是有帮助的:

In the end a stored procedure was the solution for my problem. Here´s what helped:

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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