使用多个子查询从2个表创建视图

如何解决使用多个子查询从2个表创建视图

我有两个桌子

table song

|   ID  |   TITLE   |   AUTOR   |   CODE    |
|   1   |   title_1 |   autor_1 |   123     |
|   2   |   title_2 |   autor_2 |   1332    |
|   3   |   title_3 |   autor_3 |   3434    |

table playlist

|   ID  |   DATE        |   EVENT   |
|   1   |   2020-05-01  |   123     |
|   2   |   2020-05-02  |   3434    |
|   3   |   2020-09-23  |   123     |

现在我创建一个VIEW，因为表非常大

CREATE OR REPLACE VIEW View_song
AS
select c.id,c.title,c.autor,c.code,( select
count(p.event) from playlist p
where p.event =  c.code
) as total_counter
from song c

所以我有一个VIEW，其中有歌曲总数+栏total_counter

|   ID  |   TITLE   |   AUTOR   |   CODE    |   total_counter   |  
|   1   |   title_1 |   autor_1 |   123     |       2           |
|   2   |   title_2 |   autor_2 |   1332    |       0           |
|   3   |   title_3 |   autor_3 |   3434    |       0           |

我想在VIEW中添加一列，所以我想在Today_counter中增加一列

|   ID  |   TITLE   |   AUTOR   |   CODE    |   total_counter   |  today_counter    |
|   1   |   title_1 |   autor_1 |   123     |       2           |       0           |
|   2   |   title_2 |   autor_2 |   1332    |       0           |       0           |
|   3   |   title_3 |   autor_3 |   3434    |       0           |       1           |

我尝试这个查询

CREATE OR REPLACE VIEW View_song
AS
select c.id,( select
count(p.event) from playlist p
where p.event =  c.code
) as total_counter
( select
count(p.event) from playlist p
where p.event =  c.code AND date = CURDATE()
) as today_counter
from song c

但这不起作用

解决方法

一次性使用GROUP BY进行这些计算。

CREATE OR REPLACE VIEW View_song
AS

SELECT 
    c.id,c.title,c.author,c.code,COUNT(p.`event`) AS total_counter,SUM(IF(p.`date` = CURDATE(),1,0)) AS today_counter
FROM song c
LEFT JOIN playlist p ON c.`code` = p.`event`
GROUP BY c.id;

在date，code和event上添加索引以使其更快。

在您的查询中，total_counter后也缺少逗号。