mysql GROUP_CONCAT DISTINCT multiple columns

Question

I have a tag field for a blog posts. tags have unique id but their displayName might be duplicated. What I want is a query that selects posts and in all_tags<\/code> field we get couples of (id,displayName) is this way:

id1,name1;id2,name2;id3,name3

Answer 1

Try this:

GROUP_CONCAT(
  DISTINCT CONCAT(tags.id,',',tags.displayName) 
  ORDER BY posts.id 
  SEPARATOR ';'
)

Answer 2

As advised by @Willa, I add my comment as an anwser :

GROUP_CONCAT allows you to concat multiple fields :

GROUP_CONCAT(tags.id, ',', tags.displayName)

The only difference with Stephan's answer is in case your code allows the same tag to be affected several times to one post OR if you JOIN sequence leads you to multiselect the same record in the tag table. In those case, my solution will return the same tags multiple times.

Answer 3

On top of @Stephan<\/a> 's great answer, to prevent the same content showing up multiple times due to multiple JOIN's in your query but you don't want the id to show in the output...<\/strong>

GROUP_CONCAT(
    DISTINCT
    tags.displayName,
    '||__', tags.id, '__||'
    SEPARATOR '\n'
)