我可以从一个表中显示2个字段，还可以从另一个表中显示一个计数行

Question

基本上我想展示来自UserName的UserEmail，td_users以及UserEmail中没有相同td_add_service的行。我的表格结构如下

table td_users

id | UserName | UserEmail| 
------------------------------
1  | abdul   | [email protected]
------------------------------
2  | Rahim   | [email protected]
------------------------------
3  | Karim   | [email protected]
------------------------------

table  td_add_service
    ---------------------------------------------------
id | serviceName |  serviceDeatails        | UserEmail| 
------------------------------------------------------
1  | Servi1      |   testserviceone        | [email protected]
--------------------------------------------------------------
2  | Servi11     | testserviceonev         | [email protected]
---------------------------------------------------------------
3  | Servi111    |  testserviceone1        | [email protected]
---------------------------------------------------------------
4  | Servi111    |  testserviceone2        | [email protected]
---------------------------------------------------------------

id是两个表的主键

我想显示数据

    ---------------------------------------------------
  Username |  UserMail            | No of Services| 
------------------------------------------------------
  Abdul  |  [email protected]       | 1
------------------------------------------------------
Rahim    | [email protected]        | 1
---------------------------------------------------
Karim    |  [email protected]       | 2
---------------------------------------------------

我可以从一个表和两个表中检索数据，但不能显示计数数据。

Answer 1

在任何时候使用关系表与int参数但没有nchar例如你的表与电子邮件的关系 - 这是char列

create table #td_users
(id int not null identity(1,1),
 usename nchar(10),
 email nchar(20)
 )

 create table #td_add_service
(id int not null identity(1,1),
 serviceName nchar(10),
 serviceDeatails nchar(20),
 UserEmail nchar(20)
 )

 insert into #td_users(usename,email)
 values
 ('abdul','[email protected]'),
 ('Rahim ','[email protected]'),
 ('Karim ','[email protected]');

 insert into #td_add_service(serviceName,serviceDeatails,UserEmail)
 values
 ('Servi1','testserviceone','[email protected]'),
('Servi11','testserviceonev','[email protected]'),
('Servi111','testserviceone1','[email protected]'),
('Servi111','testserviceone2','[email protected]');


select  tu.usename,
td.UserEmail,
count(td.serviceDeatails) [No of service] from #td_add_service td left join #td_users tu 
on td.UserEmail=tu.email
group by tu.usename,td.UserEmail order by 3


usename       UserEmail       No of service
abdul       [email protected]         1
Rahim       [email protected]         1
Karim       [email protected]         2

Answer 2

SELECT `td_users`.`UserName` AS Username, `td_users`.`UserEmail` AS UserMail, t2.countgroups AS NoOfServices FROM `td_users` LEFT OUTER JOIN (SELECT `id`,COUNT(*) AS countgroups FROM `td_add_service` GROUP BY `UserEmail`) t2 ON `td_users`.`id` = t2.`id`

我想这就是你问的问题。