sqlserver - mysql如何查询多列重复的数据个数？

Question

期望输出
q1	count1	q2	count2
B	2	B	1
D	1	C	2

只会差寻一列，求教如何查询多列数据重复个数！

Answer 1

My opinion is that after the database simply extracts data, it needs to be processed on the business side, and writing various complex select queries affects the efficiency

Answer 2

select distinct q1,t1.count1,tt.q2,tt.count2 ... from t
left join (select q1,count(1) count1 from t group by q1) t1 on t1.q1 = t.q1
full join (
    select distinct q2,t2.count2 from t
    left join (select q2,count(1) count1 from t group by q2) t2 on t2.q1 = t.q1
) tt on tt.q2 = t.q1 ...

I feel so vulgar, waiting for God to come.

Answer 3

select a.*,b.q2,b.q2Count,c.q3,c.q3Count from
  (SELECT (@n1:=@n1+1) as id,q1,count(*) AS q1Count FROM t1 GROUP BY q1) a
, (SELECT (@n2:=@n2+1) as id,q2,count(*) AS q2Count FROM t1 GROUP BY q2) b
, (SELECT (@n3:=@n3+1) as id,q3,count(*) AS q3Count FROM t1 GROUP BY q3) c
,(select @n1:=0,@n2:=0,@n3:=0) i
where a.id=b.id and c.id=a.id

2 D 1 B 2 D 2
1 B 3 C 2 E 1