寻找有关SQL查询的帮助

Question

我正在寻找更好的方式从我的sql表中检索数据。

Table 1: User data 
- User Id 
- User Created date 

Table 2: Mapping of the user with a role 
- User Id 
- Role 

Table 3 
Role definition 

Table 4 (may or may not have user data based on his activities on the site) 
User data 
Eg. 
- User Id 
- Total counts of the number of visits made on the portal 

我期待写（优选1）的查询量最少做以下

* 我想打印的顶级用户对每个谁拥有最高总数的角色类型的*

输出会读类似以下内容：

Header UserId---Rolename--Total Count 
Row1 Test1 ---Staff --1293 
Row2 Test2 ---Faculty --1223 
Row3 Test3 ---Dean --2283928 

有什么建议？

Answer 1

这是你在找什么：

SELECT a.UserId, b.Role, c.TotalCount 
FROM TABLE1 as a join Table2 as b on a.UserId = b.UserId 
       join Table 4 as c on a.UserId = c.UserId 
ORDER BY c.TotalCount DESC 
LIMIT 3