oracle sql 查询问题（按 2 列分组）
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oracle sql query question(grouping by 2 columns)
提问by csuo
I have a table called testgroupin my database, which is like following:
testgroup我的数据库中有一个表，如下所示：
I J
---------------------- ----------------------
1 a
1 a
2 a
1 b
1 c
2 b
3 d
2 b
2 b
3 d
Now, I want the result as below:
现在，我想要的结果如下：
I J COUNT(J) in I
---------------------- ---------------------- ----------------------
1 a 2
2 a 1
1 b 1
1 c 1
2 b 3
3 d 2
...where count(j) in Iis the number of each J related to the I.
For example: with I = 1, there are 2 ain column J, so the third column would be equal 2.
... 其中count(j) in I是与 I 相关的每个 J 的数量。
例如：有I = 1，aJ 列中有 2 个，因此第三列将等于 2。
回答by Johan
select I, J, count(*) as JinI
FROM atable
GROUP BY I, J
回答by Farshid Zaker
In fact the question is about counting I and J pairs:
事实上，问题是关于计算 I 和 J 对：
select I, J, count(*) from tblName group by I, J
