[英]get left table rows from right table conditions
我有三个这样的表:
人:
id | name | gender --------------------------- 1 Joe male 2 Daniel male 3 Sarah female
person_skills:
person_id | skill_id --------------------------- 1 1 1 2 1 3 2 1 2 2 ...
技巧:
id | skill_name ----------------------- 1 Writing 2 Programming 3 Singing ...
当我在查询中仅发送某人的技能时,我需要获得他们的所有技能。
这是我的代码:
SELECT a.name, a.gender,
GROUP_CONCAT(DISTINCT c.skill_name),
GROUP_CONCAT(DISTINCT c.id as skill_id)
FROM persons a
LEFT JOIN person_skills b ON b.person_id = a.id
LEFT JOIN skills c ON c.id = b.skill_id
WHERE b.skill_id = 3 GROUP BY a.id
我想要结果:
name | gender | skill_name | skill_id ---------------------------------------------- Joe male Writing 1 Programming 2 Singing 3
但是此代码仅返回skill_id“ 3”和skill_name“ Singing”。
提前致谢。
您需要两次引用一些表。
SELECT p.name, p.gender,
GROUP_CONCAT(DISTINCT s.skill_name),
GROUP_CONCAT(DISTINCT s.id as skill_id)
FROM person_skills AS ps0
INNER JOIN persons AS p ON ps0.person_id = p.id
LEFT JOIN person_skills ps ON p.id = ps.person_id
LEFT JOIN skills s ON s.id = ps.skill_id
WHERE ps0.skill_id = 3
GROUP BY p.id
旁注:我没有理会,但是在某些配置下您的分组条件可能会出现问题。
...以及另一种选择,如果您不喜欢多余的表引用,但是不太可能更快:
SELECT p.name, p.gender,
GROUP_CONCAT(DISTINCT s.skill_name),
GROUP_CONCAT(DISTINCT s.id as skill_id)
FROM persons AS p
LEFT JOIN person_skills ps ON p.id = ps.person_id
LEFT JOIN skills s ON s.id = ps.skill_id
GROUP BY p.id
HAVING COUNT(CASE s.skill_id WHEN 3 THEN 1 ELSE NULL) > 0;
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