mysql - 按 2 列分组并第一次出现第 3 列的 SQL 查询

Question

我不擅长 SQL 查询，所以我想在这里问一下。我有一张表 my_table:

NOTE : Consider all the columns as strings. I just represent them as numbers here for a better understanding.

A B C
-----
1 2 3
2 2 3
2 5 6
3 5 6

我希望结果是-

A B C
-----
1 2 3
2 5 6

基本上，删除 B, C 的重复对，并为那对 B, C 取第一次出现的 A。

Answer 1

看来您需要考虑列的最小值 A并按 B 分组和 C :

select min(cast(A as unsigned)) as A, cast(B as unsigned) as B, cast(C as unsigned) as C
  from my_table
 group by B , C 

cast(<column> as unsigned)转换用于使它们成为数字。

Demo