mysql - SQL select with with multiple rows for a ID

Question

我有两个表:

表 1:“用户字段”

id  name
1   age
2   birthdate
3   firstname

表 2:'user_data'

user_id user_field_id value
22          1           50
22          2           01.01.1990
22          3           Peter
25          1           33
25          2           05.08.1970
25          3           Steve

现在我想创建一个 sql 语句来显示每个 user_id 的名字和生日

示例行:

22    Peter    01.01.1990
25    Steve    05.08.1970

选择应该是什么样子的？非常感谢!

Answer 1

您需要连接表(如果您不想对值进行硬编码)，然后执行聚合:

SELECT  ud.user_id,
        MIN(CASE WHEN uf.name = 'firstname' THEN ud.value END) as firstname,
        MIN(CASE WHEN uf.name = 'birthday' THEN ud.value END) as birthday
FROM user_data ud
INNER JOIN user_fields uf
    ON ud.user_field_id = uf.user_field_id 
GROUP BY ud.user_id;

好的，根据您的新要求，一个简单的 JOIN 就可以:

SELECT  ud.user_id,
        MIN(CASE WHEN uf.name = 'firstname' THEN ud.value END) as firstname,
        MIN(CASE WHEN uf.name = 'birthday' THEN ud.value END) as birthday,
        MIN(ac.status) as status
FROM user_data ud
INNER JOIN user_fields uf
    ON ud.user_field_id = uf.user_field_id 
LEFT JOIN api_calls ac
    ON ud.user_id = ac.user_id
GROUP BY ud.user_id;