Mysql SQL-如何组合这三个SQL查询？

我是SQL新手，需要结合三个SQL查询的帮助

问题1

结果是3在本例中，该值将用于查询2中

问题2

这个结果是1。在这个例子中，这个值将在查询3中使用

问题3

以下是表格的结构：

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`);

我需要从查询中了解所有三个值。最高液位、最高运行和通过的液位

---

谢谢你的帮助

尝试如下查询：

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);

---

事实上，这是相当低效的，但它应该做你需要的

这是您要查找的查询：

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

---

希望这将对您的问题有所帮助。

查询是否有结果输出

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);

---

这三者的结合不会比单独执行更有效。事实上，在任何一个DBMS引擎中，我知道你不应该把它们结合起来，因为它们有一个不同的where子句。请在一个用例类型的故事中描述它的需要，而不是有人能够帮助你。如果没有它，至少我很难想象一个itIs id/level/run unique的用例，最后一个查询是否总是返回一行？@PeterLang id+date将是唯一的。id+级别+运行不是唯一的。最后一个查询应该只返回一行。您是否可以按级别DESC进行单个选择，运行DESC并使用LIMIT检索第一行？这只会给我级别PASSED的值。我需要知道这三种价值观。谢谢。@noc2spamツ LEVEL=3不应硬编码，因为LEVEL的值是查询的结果1@Karolis是的，我现在明白了。这最好单独实施。

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);

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

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);