mysql - 无法声明变量 SQL

Question

我一直在尝试声明一个整数变量，但它只是不起作用。这是我的查询：

DECLARE @count INT
SET     @count = 5633

SELECT count(matchid) 
FROM   `matches`
WHERE   id = @count

我收到此错误：

Error Code: 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 'DECLARE @count INT
SET     @count = 5633

请帮忙 ：）

Answer 1

根据MySQL 手册，DECLARE 只允许在 BEGIN ... END 块内，并且必须在开头。您还忘记了每行末尾的分号。这应该适合你：

SET @count = 5633;

SELECT count(*) 
FROM matches
WHERE id = @count;

COUNT(*)在某些情况下更快。

Answer 2

DECLARE @count INT;
SET     @count = 5633;

SELECT count(matchid) 
FROM   matches
WHERE   id = @count;

此外，您显然需要一个开始/结束块。

Answer 3

How about doing it all in-line

SELECT
      count(matchid) 
   FROM   
      `matches`,
      ( select @count := 5633 ) SQLVars
   WHERE   
      matches.id = @count

but more direct would otherwise, just have it directly in the WHERE clause.

Answer 4

DECLARE @count INT
SET     @count = 5633

SELECT count(matchid) 
FROM    matches  //<===  should be table name
WHERE   id = @count