從具有多對多關係的表中檢索數據？

Question

現在我該如何選擇表2爲tm_id = 10

，什麼是做這個任務的最佳途徑PROJECT_TITLE？

Answer 1

SELECT t2.project_title FROM table2 AS t2 
JOIN table3 AS t3 ON t3.project_id = t2.project_id 
WHERE t3.tm_id = 10; 

Answer 2

我認爲一個簡單的INNER JOIN就足夠你的需要。

SELECT a.*, c.project_title 
FROM Online_team a 
     INNER JOIN team_project b 
      ON a.tm_id = b.tm_id 
     INNER JOIN online_team_projects c 
      ON b.project_ID = c.project_ID 
WHERE a.tm_id = 10 

爲了進一步獲得更多的知識有關加入，請訪問以下鏈接：

• Visual Representation of SQL Joins

但是，如果你不從Online_team需要任何列，您可以將其刪除從連接列表中刪除。

SELECT c.project_title 
FROM team_project b 
     INNER JOIN online_team_projects c 
      ON b.project_ID = c.project_ID 
WHERE b.tm_id = 10 

Answer 3

SELECT 
    otp.project_title 
FROM online_team_projects otp, 
    team_project tp 
WHERE otp.project_id = tp.project_id 
    AND tp.tm_id = 10 

Answer 4

使用查詢，如下

SELECT table2.project_title from table2,table3 where table2.project_id = table3.project_id and table3.tm_id = 10 

Answer 5

你可以使用這種方法：

SELECT otp.project_title 
FROM online_team ot 
INNER JOIN online_team_projects otp USING (project_id) 
WHERE ot.tm_id = 10