在两个字段上使用 group by 并在 SQL 中计数

Using group by on two fields and count in SQL(在两个字段上使用 group by 并在 SQL 中计数)

问题描述

我的 mysql 数据库中有一个表，它有两列:组和子组.见下文.

 组，子组grp-A, sub-Agrp-A, sub-Agrp-A, sub-Bgrp-B, sub-Agrp-B, sub-Bgrp-B, sub-B

我正在尝试获取每个唯一情侣组/子组的记录数.

这是我所期望的:

组、子组、计数grp-A, sub-A, 2grp-A, sub-B, 1grp-B, sub-A, 1grp-B, sub-B, 2

在阅读了一些帖子后，我尝试了使用 group by、count() 的几个 sql 查询，但我没有得到预期的结果.我该如何解决这个问题?

我想你在找:SELECT a, b, COUNT(a) FROM tbl GROUP BY a, b>

I have a table in my mysql db that has two columns: group and subgroup. See below.

 group, subGroup
 grp-A, sub-A
 grp-A, sub-A
 grp-A, sub-B      
 grp-B, sub-A
 grp-B, sub-B
 grp-B, sub-B

I am trying to get the number of records for each unique couple group/subGroup.

This is what I expect:

group, subGroup, count
grp-A, sub-A, 2
grp-A, sub-B, 1
grp-B, sub-A, 1
grp-B, sub-B, 2

After reading some posts I tried several sql queries using group by, count(), but I do not manage to get the expected result. How can I fix this?

I think you're looking for: SELECT a, b, COUNT(a) FROM tbl GROUP BY a, b

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