使用連接從2個表中獲取不同的數據

Question

以下是我的查詢。我從Employee表中取得socail sercurity no，並將其與child_excel表匹配。使用該工具，我獲得了Employee ID並將其與EmployeeCh表（具有員工ID）進行匹配。員工有兩個孩子，所以當我把性別條款放在一起時，我爲每個孩子的每個孩子（即男性，女性）得到4條記錄2。我只想爲每個孩子分配兩個孩子，每個孩子都有兩個不同的性別。

SELECT distinct 
     [SSN], 
     empch2.GenderID, 
     gen.Name1 
    FROM [child_excel] as t 
    INNER JOIN Employee as empch on t.SSN = empch.SocialSecurityNo 
    INNER JOIN EmployeeCh as empch2 on empch.ID = empch2.EmployeeID 
    INNER JOIN Gender as gen on empch2.GenderID = gen.ID 

我得到O/P爲

12345 1 Male 
12345 2 Female 
99999 1 Male 
99999 2 Female 

預計產量

12345 1 Male 
99999 2 Female 

但是，當我在加入添加名字它給適當的輸出。我硝基甲苯想用的名字

SELECT distinct 
      [SSN], 
      empch2.GenderID, 
      gen.Name1 
     FROM [child_excel] as t 
     INNER JOIN Employee as empch on t.SSN = empch.SocialSecurityNo 
     INNER JOIN EmployeeCh as empch2 on empch.ID = empch2.EmployeeID and t.First_Name= empch2.FirstName 
     INNER JOIN Gender as gen on empch2.GenderID = gen.ID 

Answer 1

使用ROW_NUMBER（）

Select * from (

SELECT distinct 
     [SSN], 
     empch2.GenderID, 
     gen.Name1, 
     ROW_NUMBER()OVER(PARTITION BY [SSN] ORDER BY empch2.GenderID)RN 
    FROM [child_excel] as t 
    INNER JOIN Employee as empch on t.SSN = empch.SocialSecurityNo 
    INNER JOIN EmployeeCh as empch2 on empch.ID = empch2.EmployeeID and t.First_Name= empch2.FirstName 
    INNER JOIN Gender as gen on empch2.GenderID = gen.ID)T 
    WHERE T.RN = 1