如何在Mysql中针对唯一ID获取每个值的计数

Question

我有下面提到的表：

其中Val列有3个不同的值a，b＆amp;角

ID     Val
1      a
1      a
1      b
2      b
2      c
2      c
3      c

我想得到各个Val值（即a，b＆amp; c）的唯一ID和id数。

我正在使用这样的查询，但它有助于我一次识别单个Val值的计数。

SELECT ID,COUNT(*) 
FROM table1
WHERE Val='c' GROUP BY ID;

必需的输出：

ID      count    a     b    c
1       3        2     1    0
2       3        0     1    2      
3       1        0     0    1

Answer 1

只需使用条件聚合：

select id, count(*), sum(val = 'a') as a, sum(val = 'b') as b, sum(val = 'c') as c
from table1
group by id;

Answer 2

当val等于a，b或c时，您可以使用group by并对计数求和。见下文：

select id, 
    count(*) as `count`, 
    sum(case when val = 'a' then 1 else 0 end) as a, 
    sum(case when val = 'b' then 1 else 0 end) as b, 
    sum(case when val = 'c' then 1 else 0 end) as c
from yourTable
group by id;