I have a table in my mysql db that has two columns: group and subgroup. See below.
我的mysql db中有一个表，它有两列:group和subgroup。见下文。
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.
我正在尝试为每个特殊的组/子组获取记录的数量。
This is what I expect:
这就是我所期望的:
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?
在阅读了一些帖子之后，我使用group by, count()来尝试了几个sql查询，但是我没有得到预期的结果。我该怎么解决这个问题呢?
3 个解决方案
#1
113
I think you're looking for: SELECT a, b, COUNT(a) FROM tbl GROUP BY a, b
我想你在寻找:从tbl组中选择a, b, COUNT(a) BY a, b
#2
6
SELECT group,subGroup,COUNT(*) FROM tablename GROUP BY group,subgroup
#3
6
You must group both columns, group and sub-group, then use the aggregate function COUNT().
必须对列、组和子组进行分组，然后使用聚合函数COUNT()。
SELECT
group, subgroup, COUNT(*)
FROM
groups
GROUP BY
group, subgroup
#1
113
I think you're looking for: SELECT a, b, COUNT(a) FROM tbl GROUP BY a, b
我想你在寻找:从tbl组中选择a, b, COUNT(a) BY a, b
#2
6
SELECT group,subGroup,COUNT(*) FROM tablename GROUP BY group,subgroup
#3
6
You must group both columns, group and sub-group, then use the aggregate function COUNT().
必须对列、组和子组进行分组，然后使用聚合函数COUNT()。
SELECT
group, subgroup, COUNT(*)
FROM
groups
GROUP BY
group, subgroup