计算 MySql 中的多列

Question

Table "orc"

P1        p2       p3         p4
__________________________________
w2        w2       w2         w1
w1        w5       w3         w7

Table "artg"

ref      design
_________________
w1        product1
w2        product2  
w3        product3
w4        product4
w5        product5
w6        product6
w7        product7

我需要把P1、P2、P3、P4一起数。

点赞输出：

Design    Total
_________________
Product1     2
Product2     3

Answer 1

使用Union All将orctable的所有列合并为一列。然后找到每个设计的数量并加入 artg table.

查询

select t2.design,count(t1.p) as Total 
from
(
    select p1 as p from orc
    union all
    select p2 as p from orc
    union all
    select p3 as p from orc
    union all
    select p4 as p from orc
)t1
right join artg t2
on t1.p = t2.ref
group by t2.design;

结果

+----------+-------+
| Design   | Total |
+----------+-------+
| product1 | 2     |
| product2 | 3     |
| product3 | 1     |
| product4 | 0     |
| product5 | 1     |
| product6 | 0     |
| product7 | 1     |
+----------+-------+

计算 MySql 中的多列

Count multiple columns in MySql

mysql

count