SQL查詢以獲得期望的結果

Question

我有2個表。我要爲輸出MySQL查詢中的截圖：

有什麼解決方案嗎？

Answer 1

試試這個：

SELECT Table_1.Firstname, Table_2.Lastname, Table_2.RF1 AS 'RaterFirst', Table_2.RL1 AS 'RaterLast' FROM Table_1, Table_2 WHERE (Table_1.ID = Table_2.ID) 
UNION 
SELECT Table_1.Firstname, Table_2.Lastname, Table_2.RF2 AS 'RaterFirst', Table_2.RL2 AS 'RaterLast' FROM Table_1, Table_2 WHERE (Table_1.ID = Table_2.ID) 
UNION 
SELECT Table_1.Firstname, Table_2.Lastname, Table_2.RF3 AS 'RaterFirst', Table_2.RL3 AS 'RaterLast' FROM Table_1, Table_2 WHERE (Table_1.ID = Table_2.ID) 

但我想告訴你，這是不是在設計數據庫表TABLE_2 你必須保持多行記錄每個ID的正確方法。 檢查First Normal Form

Answer 2

您可以使用此：

Select Firstname, Lastname, Table_2.RF1 AS Raterfirst, Table_2.RL1 AS Raterlast 
From Table_1 
Inner Join Table_2 
ON Table_1.ID = Table_2.ID 
WHERE Raterfirst <> '' OR Raterlast <> '' 

UNION 

Select Firstname, Lastname, Table_2.RF2 AS Raterfirst, Table_2.RL2 AS Raterlast 
From Table_1 
Inner Join Table_2 
ON Table_1.ID = Table_2.ID 
WHERE Raterfirst <> '' OR Raterlast <> '' 

UNION 

Select Firstname, Lastname, Table_2.RF3 AS Raterfirst, Table_2.RL3 AS Raterlast 
From Table_1 
Inner Join Table_2 
ON Table_1.ID = Table_2.ID 
WHERE Raterfirst <> '' OR Raterlast <> '' 

您可以優化SQL命令，例如只使用一個Where表達。