是否可以使用MySQL以這種方式對行進行分組？

Question

我有一個MySQL表所示：

ID, USER, PARAM, VAL 
-------------------- 
1 | 1 | NAME | ADAM 
2 | 1 | AGE | 15 
3 | 2 | NAME | EVA 
4 | 2 | AGE | 16 
5 | 3 | NAME | CRISS 
6 | 3 | AGE | 14 

，我很好奇，如果有這將使我類似的東西一個查詢：

1 | ADAM | 15 
2 | EVE | 16 
3 | CRISS| 14 

到目前爲止，我只是用下面的查詢和分組循環中的記錄。

SELECT * FROM table WHERE PARAM ='NAME' OR PARAM = 'AGE' 

我試圖使用GROUP但沒有成功。

Answer 1

你可以做一個查詢這樣的：

SELECT t1.user, 
     (
      SELECT val FROM tab1 t2 
      WHERE t2.user = t1.user 
      AND t2.param = 'Name' 
     ) name, 
     (
      SELECT val FROM tab1 t2 
      WHERE t2.user = t1.user 
      AND t2.param = 'Age' 
     ) age 
    FROM tab1 t1 
    GROUP BY user 

另一種可能性是GROUP_CONCAT，但你都值一個列聽。

SELECT user, group_concat(param, ':', val) 
    FROM tab1 
    GROUP BY user 

Answer 2

使用同一個表聯接：

SELECT a.USER user_id, a.VAL user_name, b.VAL user_age 
FROM `table` a 
INNER JOIN `table` b ON a.USER = b.USER 
WHERE a.PARAM = 'NAME' 
AND b.PARAM = 'AGE' 

結果：

user_id  user_name user_age 
1   ADAM  15 
2   EVA   16 
3   CRISS  14 

Answer 3

嗨，我複製你的問題在我的分貝例如，嘗試此查詢：

SELECT t1.USER,VAL,(SELECT VAL AS AGE FROM table1 where USER = t1.USER AND PARAM = 'AGE') as AGE 
    FROM table1 t1 
    WHERE param = 'NAME' 

或在您的餐桌上使用加入：

SELECT a.USER, a.VAL, b.VAL 
FROM table1 t1 
INNER JOIN table1 t2 
ON t1.USER = t2.USER 
WHERE t1.PARAM = 'NAME' 
AND t2.PARAM = 'AGE' 

用你的表名替換table1。

Answer 4

您可以生成使用最常用的技術樞軸視圖

select 
user, 
max(case when param = 'NAME' then val end) as name, 
max(case when param = 'AGE' then val end) as age 
from mytable 
group by user 

Answer 5

有沒有必要使用JOIN。試試這個：

SELECT USER, 
     MAX(CASE PARAM WHEN 'NAME' THEN VAL ELSE NULL END) AS NAME, 
     MAX(CASE PARAM WHEN 'AGE' THEN VAL ELSE 0 END) AS AGE 
FROM test 
GROUP BY USER;