选择2个差异的行MySQL

我有一个名为category的表,该表具有3列：id,name,parent_id.

ID         name         group_id
==         ==           ==
1          haim         1
2          gil          2
3          alon         1
4          idan         1
5          shai         3
6          adi          2
7          itay         3
8          aviram       1
9          lioz         3
10         amit         2
11         ben          2
12         eran         1

我必要在一个查询中选择每个group_id 2行,以是功效将是：

ID         name         group_id
==         ==           ==
1          haim         1
3          alon         1
2          gil          2
6          adi          2
5          shai         3
7          itay         3

很是重要的一点是,它也将按group_id举办排序.

感谢！

SELECT ID,NAME,GROUP_ID
FROM MYTABLE WHERE ID IN (
    SELECT MIN(ID)
    FROM MYTABLE
    GROUP BY GROUP_ID)

UNION ALL

SELECT ID,GROUP_ID
FROM MYTABLE WHERE ID IN (
    SELECT MIN(ID)
    FROM MYTABLE
    WHERE ID NOT IN (
      SELECT MIN(ID)
      FROM MYTABLE
      GROUP BY GROUP_ID
      )
    GROUP BY GROUP_ID)
ORDER BY GROUP_ID

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