mysql - 在Mysql中使用sql count multiple columns yes and no

Question

我有一些数据，有没有简单的方法？

create table tb_count(
    id int not null auto_increment,
    col1 enum('yes', 'no'),
    col2 enum('yes', 'no'),
    col3 enum('yes', 'no'),
    col4 enum('yes', 'no'),
    primary key(id)
) default charset=utf8;

insert into tb_count values (null, 'yes', 'yes', 'no', 'yes');
insert into tb_count values (null, 'no', 'yes', 'no', 'no');
insert into tb_count values (null, 'no', 'yes', 'no', 'yes');
insert into tb_count values (null, 'no', 'no', 'no', 'no');

select * from tb_count;

enter image description here

# I want to get the following output：
# value col1  col2  col3  col4
# yes    1      3    0      2
# no     3      1    4      2

顺便说一句，我有一个更复杂的方法，我不想使用union all

我的代码

SELECT
    'yes' AS 'value',
    SUM( CASE WHEN col1 = 'yes' THEN 1 ELSE 0 END ) AS col1,
    SUM( CASE WHEN col2 = 'yes' THEN 1 ELSE 0 END ) AS col2,
    SUM( CASE WHEN col3 = 'yes' THEN 1 ELSE 0 END ) AS col3,
    SUM( CASE WHEN col4 = 'yes' THEN 1 ELSE 0 END ) AS col4 
FROM
    tb_count
    UNION ALL
SELECT
    'no' AS 'value',
    SUM( CASE WHEN col1 = 'no' THEN 1 ELSE 0 END ) AS col1,
    SUM( CASE WHEN col2 = 'no' THEN 1 ELSE 0 END ) AS col2,
    SUM( CASE WHEN col3 = 'no' THEN 1 ELSE 0 END ) AS col3,
    SUM( CASE WHEN col4 = 'no' THEN 1 ELSE 0 END ) AS col4 
FROM
    tb_count

我想知道这样做是否是一种好的做法，什么是最好的做法？

Answer 1

这是另一种方法:

SELECT 
  IF(y.yn=1,'yes','no')
, SUM(y.yn = col1) AS col1
, SUM(y.yn = col2) AS col2
, SUM(y.yn = col3) AS col3
, SUM(y.yn = col4) AS col4
FROM `tb_count` AS t
JOIN (SELECT 1 AS yn UNION ALL SELECT 2)  AS y
GROUP BY y.yn;