Mysql的與GROUP BY + IF +左+加入GROUP_CONCAT

Question

我覺得它如此微不足道，但我還是堅持了這一點：

SELECT u.id, u.name, 

IF(s.prod_id=0, 1,NULL) as amount, 
IF(s.prod_id=92, 2,NULL) as amount2, 
IF(s.prod_id=116, 3,NULL) as amount3, 
IF(s.prod_id=134, 4,NULL) as amount4 

FROM table_user u 

LEFT JOIN table_user_status s ON s.user_id = u.id 
where s.prod_id = 0 OR s.prod_id = 92 OR s.prod_id = 117 OR s.prod_id = 134 

-- GROUP BY u.id 
order by u.id ASC 

我得到的是這樣的：

22 | Matt | 1|NULL|NULL|NULL 

22 | Matt | NULL|2|NULL|NULL 

集團後編號我得到22 MATT 1 NULL NULL NULL，然後下一個記錄。

在結束我必須爲數據用戶GROUP_CONCAT像 22 | Matt | 1,2 |

謝謝！

Answer 1

使用CASE表達對所有這些案件返回爲一列，然後只是GROUP_CONCAT它：

SELECT 
    u.id, 
    u.name, 
    GROUP_CONCAT(amount ORDER BY amount) amounts 
FROM 
(
    SELECT 
     u.id, 
     u.name, 
     CASE s.prod_id 
      WHEN 0 THEN 1 
      WHEN 92 THEN 2 
      WHEN 116 THEN 3 
      WHEN 134 THEN 4 
     END AS amount 
    FROM table_user u 
    LEFT JOIN table_user_status s 
     ON s.user_id = u.id 
    WHERE s.prod_id IN (0, 92, 116, 134) 
) u 
GROUP BY 
    u.id, 
    u.name 
ORDER BY u.id