Only select if column value is unique?

[pmiller624]

I have three tables that when simplified are set up like below.

 

      tag_map

+--------+--------+

| user_id | tag_id |

+--------+--------+

|    1    |    1    |

|    2    |    1    |

|    2    |    2    |

/*etc*/

 

    tags

+--+---------+

| id |  name  |

+--+---------+

| 1 |    PHP  |

| 2 |  mySQL |

/*etc*/

 

user

+--+

| id |

+--+

| 1 |

| 2 |

 

I have an sql query that looks like:

 

SELECT *

FROM tag_map

JOIN `users`

ON tag_map.user_id = users.id

WHERE tag_id = 1 OR tag_id = 2

 

If you were to run this query on the data above user 2 would come up twice because he has the tags of 1 and 2. So my question is how can I make it so the query only selects a users id number once, no matter how many times his tag pops up?

[abdfahim]

I am wondering, if you want to show every user only once, which corresponding tag_id you want to show? any one? maximum? or you dont want tag_id?

[www333]

SELECT distinct(user_id),tag_id

  FROM tag_map

  JOIN `users`

  ON tag_map.user_id = users.id

  WHERE tag_id = 1 OR tag_id = 2

 

You can " SELECT distinct(user_id)" not "tag_id"，but it's meaningless.

[dix.selken]

hello if you don't mind the value for tag you could use something like this

 

SELECT user_id, max(tag_id) tag_id

  FROM tag_map

  JOIN `users`

  ON tag_map.user_id = users.id

  WHERE tag_id in (1,2)

group by user_id