Question

我目前遇到了MySQL问题。

我有两张桌子：

TABLE1
------
id   name 
1    John

TABLE2
------
id   TABLE1_id name   value
1    1         Age    42
2    1         Height 172cm

我想得到John的所有特征：

 name age height 
 John 42  172cm

这是我当前的查询：

SELECT DISTINCT

                IF(TABLE2.name = "Age", TABLE2.value, 0) as age,

                IF(TABLE2.name = "Height", TABLE2.value, 0) as height,

FROM TABLE1

                LEFT JOIN TABLE2 ON TABLE2.TABLE1_id = TABLE1.id

WHERE

                TABLE1.name = "John"

问题是查询返回2行：一行是Age，另一行是Height。

我尝试了几种JOIN类型（LEFT，RIGHT等），尝试删除＆＃34; DISTINCT＆＃34;但是我无法解决这个问题。

你能帮忙吗？：）

Answer 1

 SELECT * FROM eav_hell;
 +----+--------+-----------+------------+
 | id | entity | attribute | value      |
 +----+--------+-----------+------------+
 |  1 |      1 | date      | 03/04/2009 |
 |  2 |      1 | shift     | 1st        |
 |  3 |      1 | station 1 | Mark       |
 |  4 |      1 | station 2 | John       |
 |  5 |      1 | station 2 | Macy       |
 |  6 |      2 | date      | 04/04/2009 |
 |  7 |      2 | shift     | 2nd        |
 |  8 |      2 | station 1 | John       |
 |  9 |      2 | Station 1 | Drey       |
 | 10 |      2 | Station 2 | Macy       |
 +----+--------+-----------+------------+
 10 rows in set (0.00 sec)


 SELECT entity
      , MAX(CASE WHEN attribute = 'date' THEN value END) date 
      , MAX(CASE WHEN attribute = 'shift' THEN value END) shift
      , GROUP_CONCAT(CASE WHEN attribute = 'station 1' THEN value END) station1
      , GROUP_CONCAT(CASE WHEN attribute = 'station 2' THEN value END) station2
   FROM eav_hell
  GROUP
     BY entity;
+--------+------------+-------+-----------+-----------+
| entity | date       | shift | station1  | station2  |
+--------+------------+-------+-----------+-----------+
|      1 | 03/04/2009 | 1st   | Mark      | John,Macy |
|      2 | 04/04/2009 | 2nd   | Drey,John | Macy      |
+--------+------------+-------+-----------+-----------+

Answer 2

这个怎么样？它只是将第一个表分别与第二个表联合起来并将结果加在一起

SELECT "Name" as `Key` ,t1.Name as `Value`
FROM Table1 t1
UNION
SELECT t2.Name as `Key`, t2.Value
FROM TABLE2 t2
INNER JOIN TABLE1 t1 on t2.Table1_ID = t1.ID
WHERE t1.Name = "John"

SQL小提琴在这里：http://sqlfiddle.com/#!2/544489/11

通过JOIN获得不同的特征

2 个答案: