Question

我试图找出如何在我的查询中添加yes / no列。这是我的情景：

模式

Table_A    Table_B
-------    -------
uid         uid
color       name

样本数据

Table_A       Table_B
uid    color   uid     name
1      red      1      Joe 
1      blue     1      Joe

查询

SELECT table_a.color,table_b.name
FROM table_a
LEFT JOIN table_b ON table_a.id = table_b.id
WHERE table_a.color LIKE 'red'

这可以按预期工作，但是，我想添加一个名为＆＃39; blue＆＃39;如果Joe有蓝色和红色，请添加一个＆＃39; Y＆＃39;否则添加一个＆＃39; N＆＃39;

预期结果

uid    color    blue
1      red      Y

Answer 1

您可以尝试以下查询来获得结果

        SELECT A.uid,A.color,case when cnt=2 then 'Y' else 'N'  end as blue
        FROM tableA as A
        LEFT JOIN (select uid as id,count(distinct color)as cnt from  tableA
        WHERE lower(color)  in ('blue', 'red') group by uid)  as B ON A.uid = B.id 
        WHERE A.color='red'

MySQL添加是/否列和过滤

1 个答案: