Mysql："SET @Variable = 0" 在一次查询中 [Java]

Question

我有两个 sql 查询。但是在 Java 中我不能设置变量。

我试图将它概括为一个查询。但这不起作用，因为 sql 语法错误。

SET @rn = 0;
SELECT * 
FROM (SELECT t.id, @rn := @rn + 1 AS rank 
      FROM stats t 
      ORDER BY t.points DESC) t2 
WHERE t2.id = ?;

Answer 1

如果只有SET部分是你可以做的问题

SELECT t.id, @rn := @rn + 1 AS rank 
FROM stats t 
CROSS JOIN ( SELECT @rn := 0 ) as parameters
ORDER BY t.points DESC

Answer 2

您需要像这样进行连接：

SELECT stats.id, @rn := @rn+1 AS rank
FROM stats, (SELECT @rn:=0) a
WHERE stats.id = ?

如果你有 mysql 8.0，你可以使用： ROW_NUMBER() or RANK() :

SELECT
   id,
   ROW_NUMBER() OVER w AS 'row_number',
   RANK()       OVER w AS 'rank',
FROM stats
WHERE stats.id = ?
WINDOW w AS (ORDER BY points);

Mysql: "SET @Variable = 0" in one query [Java]