Question

假设我有一个包含id和版本的表。我正在按ID分组。对于每个id，如果version = 2，则获取该行，否则获取MAX（版本）。

+----+---------+
| id | version |
+----+---------+
|  1 |       3 |
|  1 |       2 |
|  2 |       1 |
|  2 |       3 |
+----+---------+

应该获取

+----+---------+
| id | version |
+----+---------+
|  1 |       2 |
|  2 |       3 |
+----+---------+

查询应该是这样的：

select id, version(2 if exists for id or max) from table group by id;

我不想使用union，因为它实际上是一个带有多个连接的巨大查询。我只是用一个更简单的例子来说明问题。

可能的解决方案：

select * from (select * from table order by version = 2 desc, version desc) as t1 group by id

Answer 1

1.获取版本= 2的行;

2.获取id不在version = 2行中的最大版本行;

3.将它们分开。

试试这个：

SELECT id, version FROM table WHERE version = 2
UNION
SELECT id, MAX(version) version FROM table WHERE id not in 
(SELECT id FROM table WHERE version = 2)
GROUP BY id

SQL Fiddle

Answer 2

试试这个

select id, version from table 
where id=2 or version in 
    (select max(version) from table 
        where id!=2  group by id)

Answer 3

试试这个：

SELECT * FROM(SELECT id,versioin from table1 where version=2 
union 
SELECT id,max(version) as version FROM `table1 ` GROUP BY version) as A 
group by version

或

SELECT id,versioin from table1 where version=2 
union 
SELECT id,max(version) as version FROM `table1 ` 
where id not in(SELECT id from table1 where version=2 ) GROUP BY version

Answer 4

查看此处：

SELECT id,ver
FROM table1
WHERE ver = 
(SELECT MAX(ver) FROM table1 WHERE ver < (SELECT MAX(ver) FROM table1))
UNION
SELECT id,(MAX(`ver`)) FROM table1 WHERE id=2;

sqlfiddle：http://sqlfiddle.com/#!2/b7f65/1

MySql：Group By选择特定值或最大值

4 个答案: