MYSQL选择具有特定技能的用户

Question

我目前为止最复杂的SQL查询我做过的，这可能是非常简单的大部分你（通过得过且过我的方式

我有三个表，用户，技能和User_Skills。其中的字段应该是相当自我解释。

我想选择谁拥有符合我的标准的一个或多个技能的人。

我可以选择与技能后，我是一个用户，但我不知道有关语法查询多种技能。

我想只使用一个查询，所以我试图用GROUP_CONCAT

下面是我的SQL：

SELECT User_id, first_name, last_name, county, GROUP_CONCAT(CAST(Skill_id AS CHAR))
FROM User LEFT JOIN User_Skills ON User.id = User_Skills.User_id
LEFT JOIN Skills ON User_Skills.Skill_id = Skills.id GROUP BY User_id

---

User_id  first_name  last_name  county        GROUP_CONCAT(CAST(Skill_id AS CHAR))
1000    Joe         Blow       West Yorkshire   8,6,1,9,7,3,5,10
1001    Fred        Bloggs     COUNTY1          5,8,2,7,9
1003    asdf        asdf1      Some County      10,8,2

如何将搜索范围限制为仅谁拥有的技能5,9人？

Answer 1

SELECT  *
FROM    users u
WHERE   EXISTS
        (
        SELECT  NULL
        FROM    user_skills us
        WHERE   us.skill_id IN (5, 9)
                AND us.user_id = u.id
        LIMIT 1, 1
        )

这依赖于以下事实：(user_id, skill_id)是PRIMARY KEY或UNIQUE密钥（即不能将技能分配给用户一次以上）。

<强>更新

要返回所有技能（逗号分隔）：

SELECT  u.*,
        (
        SELECT  GROUP_CONCAT(skill_id)
        FROM    user_skills uso
        WHERE   uso.user_ud = u.user_id
        ) AS all_skills
FROM    users u
WHERE   EXISTS
        (
        SELECT  NULL
        FROM    user_skills us
        WHERE   us.skill_id IN (5, 9)
                AND us.user_id = u.id
        LIMIT 1, 1
        )

Answer 2

SELECT User_id, first_name, last_name, county, GROUP_CONCAT(CAST(Skill_id AS CHAR))
FROM User JOIN User_Skills ON User.id = User_Skills.User_id
JOIN Skills ON User_Skills.Skill_id IN (5,9)
GROUP BY User_id

如果你要防止多种技能的记录，那么你可能需要一个子查询

SELECT User_id, first_name, last_name, county,
(
    SELECT (GROUP_CONCAT(CAST(subSkill.Skill_id AS CHAR))
    FROM Skills as subSkill WHERE subSkill.skill_id = User_Skills.skill_id
    GROUP BY subSkill.skill_id
)
FROM User JOIN User_Skills ON User.id = User_Skills.User_id
JOIN Skills ON User_Skills.Skill_id IN (5,9)
GROUP BY User_id

Answer 3

为什么你就不能使用INNER JOIN就地左的加盟，并发出一个WHERE子句所需要的技能？

SELECT User_id, first_name, last_name, county, GROUP_CONCAT(CAST(Skill_id AS CHAR)) 
FROM User 
INNER JOIN User_Skills ON User.id = User_Skills.User_id 
INNER JOIN Skills ON User_Skills.Skill_id = Skills.id GROUP BY User_id
WHERE skill_id = 5 OR skill_id=9

Answer 4

下面是如何（会给你的技能5个用户和9）：

SELECT User_id, first_name, last_name, county FROM User INNER JOIN User_Skills ON User.id = User_Skills.User_id INNER JOIN Skills ON User_Skills.Skill_id = Skills.id WHERE Skills.Skill_id = 5 AND Skills.Skill_id = 9 GROUP BY User_id

Answer 5

您只需要一个

HAVING FIND_IN_SET('5', skills) AND FIND_IN_SET('9', skills)

的组由后（其中，“技能”是分组列的名称）。所以，你的查询现在看起来应该

SELECT User_id, first_name, last_name, county, GROUP_CONCAT(CAST(Skill_id AS CHAR)) as skills
FROM User LEFT JOIN User_Skills ON User.id = User_Skills.User_id
LEFT JOIN Skills ON User_Skills.Skill_id = Skills.id GROUP BY User_id
HAVING FIND_IN_SET('5', skills) AND FIND_IN_SET('9', skills)