Question

我正在使用mysql / mariadb。

我想做什么：为每个id获取name，private，Group /然后获取每个Video的数量Group 1}} /然后获取每个Video的最后20 Group个。

现在，我使用三个单独的SQL查询，然后每次为每个相应的id运行它。有没有办法将三个SQL查询合并为一个，并在ID列表上运行它们？

例如，在1,2,3组：

Executing (default): select `id`, `name`, `private` from `Groups` where `id` = '1' limit 1
Executing (default): select `id`, `name`, `private` from `Groups` where `id` = '2' limit 1
Executing (default): select `id`, `name`, `private` from `Groups` where `id` = '3' limit 1

Executing (default): select count(*) from `Videos` where `GroupId` = '1' and `live` = true
Executing (default): select count(*) from `Videos` where `GroupId` = '2' and `live` = true
Executing (default): select count(*) from `Videos` where `GroupId` = '3' and `live` = true

Executing (default): select `id`, `file` from `Videos` where `GroupId` = '1' and `live` = true order by `id` desc limit 20
Executing (default): select `id`, `file` from `Videos` where `GroupId` = '2' and `live` = true order by `id` desc limit 20
Executing (default): select `id`, `file` from `Videos` where `GroupId` = '3' and `live` = true order by `id` desc limit 20

Answer 1

使用IN

Executing (default): (SELECT `id`, `name`, `private` FROM `Groups` WHERE`id` = '1' LIMIT 1)
                     UNION ALL
                     (SELECT `id`, `name`, `private` FROM `Groups` WHERE`id` = '2' LIMIT 1)
                     UNION ALL
                     (SELECT `id`, `name`, `private` FROM `Groups` WHERE`id` = '3' LIMIT 1)

Executing (default): SELECT count(*) 
                     FROM `Videos` 
                     WHERE `GroupId` IN ('1', '2', '3')  AND `live` = true

Executing (default): (SELECT `id`, `file` FROM `Videos` WHERE`GroupId` = '1' AND `live` = true ORDER BY `id` DESC LIMIT 20)
                     UNION ALL
                     (SELECT `id`, `file` FROM `Videos` WHERE`GroupId` = '2' AND `live` = true ORDER BY `id` DESC LIMIT 20)
                     UNION ALL
                     (SELECT `id`, `file` FROM `Videos` WHERE`GroupId` = '3' AND `live` = true ORDER BY `id` DESC LIMIT 20)

是否可以组合这些SQL select语句？

1 个答案: