从同一 table mysql 存储过程中选择具有不同条件的多个计数

Question

我有一个 table 如下所示

tbl_test

test_id     name    val

1            ab       1
2            ac       1
3            ad       2
4            af       3
5            fg       2
6            ss       1
7            dd       3

我想在同一个查询中根据 val 对名称进行计数

尝试过

(select count(name )   where val='1' ) as one,
(select count(name )   where val='2' ) as two,
(select count(name )   where val='3' ) as thr

预期产出

one  two  thr

3     2   2

Answer 1

您可以将条件聚合与 case when expression -

结合使用

select 
    count(case when val=1 then name end) as one,
    count(case when val=2 then name end) as two,
    count(case when val=3 then name end) as thr
from tbl_test

从同一 table mysql 存储过程中选择具有不同条件的多个计数

Selecting multiple count with different conditions from same table mysql stored procedure

mysql

sql

mariadb

stored-functions