Question

我是SQL新手，需要帮助组合三个SQL查询。

查询1

SELECT max(level) level FROM tablename WHERE id = 1

在此示例中，结果为3，此值将用于查询2。

查询2

SELECT max(run) run FROM tablename WHERE id = 1 AND level = 3;

在此示例中，结果为1，此值将用于查询3。

查询3

SELECT levelpassed FROM tablename WHERE id = 1 AND level = 3 AND run = 1;

这是表格的结构：

CREATE TABLE `tablename` (
 `id` int(11) NOT NULL,
 `date` datetime NOT NULL,
 `level` int(11) NOT NULL,
 `run` int(11) NOT NULL,
 `cr` int(11) NOT NULL,
 `fr` int(11) NOT NULL,
 `dv` int(11) NOT NULL,
 `levelpassed` tinyint(1) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

以下是主键：

ALTER TABLE `tablename`
 ADD PRIMARY KEY (`id`,`date`);

我需要知道查询中的所有三个值。最高等级，最高行程和等级。

感谢您的帮助！

Answer 1

这是您正在寻找的查询：

SELECT *
FROM tablename T
INNER JOIN (SELECT T2.id
             ,MAX(T2.level) AS [level]
           FROM tablename T2) TL ON TL.id = T.id
                                  AND TL.level = T.level
INNER JOIN (SELECT T3.id
             ,MAX(T3.run) AS [run]
           FROM tablename T3) TL ON TR.id = T.id
                                  AND TR.run = T.run
WHERE T.id = 1

希望这可以帮助您解决问题。

Answer 2

您是否有查询结果输出？

请尝试：

select levelpassed from tablename a where id = 1 and run = (select max(run) from tablename b where a.id = b.id) and level = (select max(level) from tablename c where a.id = c.id);

Answer 3

尝试查询如下：

SELECT levelpassed ,
  (SELECT max(LEVEL) LEVEL
   FROM tablename
   WHERE id = 1) level,
  (SELECT max(run) run
   FROM tablename
   WHERE id = 1
     AND LEVEL = 3) run
FROM tablename
WHERE id = 1
  AND LEVEL =
    (SELECT max(LEVEL) LEVEL
     FROM tablename
     WHERE id = 1)
  AND run =
    (SELECT max(run) run
     FROM tablename
     WHERE id = 1
       AND LEVEL = 3);

实际上这是非常低效的，但它应该做你需要的。

SQL - 如何组合这三个SQL查询？

3 个答案: