我有一张 table :
DataTable:
id int,
user_id int,
field_id int,
value varchar
数据示例:
id user_id field_id value
1 1 1 'Peter'
2 1 2 56
3 1 3 100
4 2 1 'Buzz'
5 2 2 47
6 2 3 120
我想通过 field_id
属性分隔 value
列:
Name Age Score
Peter 56 100
Buzz 47 120
我尝试过:
SELECT
CASE
WHEN field_id = 1 THEN value
END as Name,
CASE
WHEN field_id = 2 THEN value
END as Age,
CASE
WHEN field_id = 3 THEN value
END as Score
FROM Users u
INNER JOIN DataTable t ON (t.user_id=u.id)
但是得到了:
Name Age Score
Peter null null
null 56 null
null null 100
Buzz null null
null 47 null
null null 120
有什么建议吗?
最佳答案
您可以将GROUP BY
应用于您的查询。 Name
可能不是唯一的,您可以考虑按 id
分组:
SELECT id, MAX(Name) AS Name, MAX(Age) AS Age, MAX(Score) AS Score
FROM (
SELECT u.id
CASE
WHEN field_id = 1 THEN value
END as Name,
CASE
WHEN field_id = 2 THEN value
END as Age,
CASE
WHEN field_id = 3 THEN value
END as Score
FROM Users u
INNER JOIN DataTable t ON (t.user_id=u.id)
) AS sub
GROUP BY id;
关于mysql - 如何将一列分成几列?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34342654/