尋找有關SQL查詢的幫助

Question

我正在尋找更好的方式從我的sql表中檢索數據。

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 

我期待寫（優選1）的查詢量最少做以下

* 我想打印的頂級用戶對每個誰擁有最高總數的角色類型的*

輸出會讀類似以下內容：

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

有什麼建議？

Answer 1

這是你在找什麼：

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