加入基於各表中的

Question

這裏以不同的名字出現兩種常見的列是兩個表中各表的例子：

客戶

╔══════════╦════════════╗ 
║ GROUP_ID ║ GROUP_NAME ║ 
╠══════════╬════════════╣ 
║ abc  ║ xex  ║ 
║ def  ║ tet  ║ 
╚══════════╩════════════╝ 

隊

╔════════╦════════════╗ 
║ ACT_ID ║ GROUP_NAME ║ 
╠════════╬════════════╣ 
║  44 ║ xex  ║ 
║  32 ║ tet  ║ 
╚════════╩════════════╝ 

動作

╔════╦════════════╗ 
║ ID ║ STATE ║ 
╠════╬════════════╣ 
║ 44 ║ complete ║ 
║ 58 ║ incomplete ║ 
╚════╩════════════╝ 

注意act_id表teams也存在於表actions作爲id

我要選擇有兩列的表：group_id和group_name，其中每個group_name具有帶有完整的act_idstate。

我做這樣的事情：

SELECT group_id AND group_name 
FROM clients 
WHERE group_name IN (SELECT group_name 
        FROM teams, actions 
        WHERE teams.act_id = actions.id 
         AND actions.state IS complete) 

這是正確的？

我也想到了什麼樣

SELECT group_id AND group_name 
FROM clients 
WHERE group_name IN (SELECT group_name 
        FROM teams 
        WHERE act_id IN (SELECT id 
             FROM actions 
             WHERE teams.act_id = actions.id. 
             AND state IS complete)) 

或者是上述的正確嗎？

我希望得到的表顯然是這一個：

╔══════════╦════════════╗ 
║ GROUP_ID ║ GROUP_NAME ║ 
╠══════════╬════════════╣ 
║ abc  ║ xex  ║ 
╚══════════╩════════════╝ 

Answer 1

SELECT a.* 
FROM clients a 
     INNER JOIN teams b 
      ON a.group_name = b.group_name 
     INNER JOIN actions c 
      ON b.act_ID = c.id 
WHERE c.state = 'complete' 

• SQLFiddle Demo

你的SQL查詢看到星號*意味着它將選擇所有列都可用，在這種情況下，它將全部從表clients中選擇。如果您只想選擇特定列，請使用comma來區分不是AND。例如，

SELECT a.GROUP_ID, a.GROUP_NAME 
FROM clients a 
     INNER JOIN teams b 
      ON a.group_name = b.group_name 
     INNER JOIN actions c 
      ON b.act_ID = c.id 
WHERE c.state = 'complete' 

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