Mysql "where" and "and" statement from multiple rows [duplicate] - php

Question

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Query to find posts with an exact set of tags (many-to-many relationship)
(2 answers)
Closed 9 years ago.
I have 3 tables:
users
+---------+
|id | name|
+---------+
|1 | Tom |
|2 | Adam|
+---------+
skills
+------------+
|id |name |
+------------+
|1 |baking |
|2 |driving|
|3 |etc |
+------------+
users_skills
+-----------------+
|user_id |skill_id|
+-----------------+
| 1 | 1 |
| 1 | 2 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
+-----------------+
So in result I have two users:
Tom has 1 and 2 skill
Adam hass 1 and 2 and 3 skill
I want to get all users that have exactly skill 1 and 2, so I want to get Tom. How to achieve that?
If I wanted to get users with skill 1 OR skill 2 - it's not a problem, but AND it is :(
Basically I tried to join users with users_skills table, but I get something like this:
+-----------------------+
|user_id |name |sill_id|
+-----------------------+
|1 |Tom | 1 |
|1 |Tom | 2 |
+-----------------------+
etc
so I have two rows and I don't know how to achieve AND statement here.

Answer 1

Here is the solution. The tricky part is the fact that not only has to match those skills but also NOT match any out of them.
SELECT u.id, u.name, us.skill_id FROM users u
JOIN users_skills us ON u.id = us.user_id
WHERE u.id IN (
SELECT user_id FROM users_skills
WHERE user_id NOT IN (
SELECT user_id FROM users_skills
WHERE skill_id NOT IN (1, 2)
)
GROUP BY user_id
HAVING COUNT(DISTINCT skill_id) = 2
)
Fiddle here. Note I've also added additional users and skills to test all cases.
In short: You first get rid of the ones that have additional unwanted skills and then you get rid of the ones that have less than the needed skills.
Output:
| ID | NAME | SKILL_ID |
|----|------|----------|
| 1 | Tom | 1 |
| 1 | Tom | 2 |

Answer 2

You need the DISTINCT function (and GROUP BY):
SELECT DISTINCT(u.name)
FROM users AS u
JOIN users_skills AS us
ON u.id = us.user_id
WHERE us.skillID IN (1,2)
GROUP BY u.id