下面，图老师小编带您去了解一下浅谈MySQL数据库中如何解决分组统计的问题，生活就是不断的发现新事物，get新技能~
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首先准备四张表A、B、C、D，
--------------------------------
A | B | C | D
a b | a c | a d | d e
1 1 | 1 1 | 1 A | A 1
2 2 | 1 3 | 2 B | B 2
3 4 | 1 4 | 3 C | C 3
4 6 | 2 1 | 4 D | D 4
--------------------------------
下面我们需要用一条sql语句将A表所有的列，B表对与A表a字段相关联的列求count,通过C表,将D表与A表关联起来，得到的结果如下：
1 1 3 1
2 2 1 2
3 4 0 3
4 6 0 4
Mysql语句解决：
（本文来源于图老师网站，更多请访问http://www.tulaoshi.com/bianchengyuyan/）select A.a,A.b,IFNULL(c,0) as c,D.a
from (select 1 as a,2 as b union all
select 2 as a,2 as b union all
select 3 as a,4 as b union all
select 4 as a,6 as b) as A
left outer join
(select a,count(a) as c from(
select 1 as a,3 as c union all
select 1 as a,3 as c union all
select 1 as a,3 as c union all
select 2 as a,3 as c ) B group by a) as B
on A.a=B.a
join
(select 1 as a,'A' as d union all
select 2 as a,'B' as d union all
select 3 as a,'C' as d union all
select 4 as a,'D' as d ) as C
on A.a=C.a
join(select 1 as a,'A' as d union all
select 2 as a,'B' as d union all
select 3 as a,'C' as d union all
select 4 as a,'D' as d ) as D
on D.d=C.d
来源:http://www.tulaoshi.com/n/20160219/1609756.html
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