获取多个表中的总记录作为视图表（mysql）答案

【问题标题】：Getting the total records in multiple tables as a view table (mysql)获取多个表中的总记录作为视图表（mysql）
【发布时间】：2016-09-19 10:04:33
【问题描述】：

有没有办法获取每个表中的总记录，然后将其放入视图表中。我当前的查询是

CREATE VIEW view_summary AS
SELECT COUNT(*) as total_records FROM users WHERE role_id = 2
UNION ALL
(SELECT COUNT(*) FROM users WHERE role_id = 1) 
UNION ALL
(SELECT COUNT(*) FROM problems)

输出是

total_records
1
2
1

此查询的问题我无法添加另一列来指定一行中的每个总记录。我的目标输出是

table_name | total_records
clients    | 1
admins     | 2
problems   | 1

谢谢

【问题讨论】：

标签： mysql

【解决方案1】：

将另一列添加为table name

CREATE VIEW view_summary AS
SELECT 'cleints' AS table_name,COUNT(*) as total_records FROM users WHERE role_id = 2
UNION ALL
(SELECT 'admins',COUNT(*) FROM users WHERE role_id = 1) 
UNION ALL
(SELECT 'problems',COUNT(*) FROM problems)

【讨论】：

【解决方案2】：

除了增加一个额外的列，你可以将前两个选择合并为 1 ：

CREATE VIEW view_summary AS
(SELECT CASE WHEN role_id = 2 THEN 'clients' ELSE 'admins' END as table_name,
       COUNT(*) as total_records FROM users WHERE role_id in (1,2)
GROUP BY CASE WHEN role_id = 2 THEN 'clients' ELSE 'admins' END

UNION ALL

SELECT 'problems',COUNT(*) FROM problems)

【讨论】：