SQL，计算多列然后分组

Question

我尝试在多个列中进行计数，然后按任意列中出现相同数据的总和进行分组

Source data table:

P1  P2  P3
-----------
a   b   
a   a   a
b   c   
a   b   b
b   a

我希望它显示这样的内容:

Desired query output:

     Total
   -------------
a |    6
b |    5
c |    1

Answer 1

您可以使用联合查询

SELECT x.f1,Count(x.f1) FROM
(SELECT p1 As F1 FROM table
 UNION ALL
 SELECT p2 As F1 FROM table
 UNION ALL
 SELECT p3 As F1 FROM table) x
GROUP BY x.f1