Question

I have three tables tag, page, pagetag

With the data below

page

ID      NAME 1       page 1 2       page 2 3       page 3 4       page 4 

tag

ID      NAME 1       tag 1 2       tag 2 3       tag 3 4       tag 4 

pagetag

ID   PAGEID  TAGID 1    2        1 2    2        3 3    3        4 4    1        1 5    1        2 6    1        3 

I would like to get a string containing the correspondent tag names for each page with SQL in a single query. This is my desired output.

ID      NAME       TAGS 1       page 1     tag 1, tag 2, tag 3 2       page 2     tag 1, tag 3 3       page 3     tag 4 4       page 4     

Is this possible with SQL?

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I am using MySQL. Nonetheless, I would like a database vendor independent solution if possible.

Answer 1

Sergio del Amo:

However, I am not getting the pages without tags. I guess i need to write my query with left outer joins.

SELECT pagetag.id, page.name, group_concat(tag.name) FROM (     page LEFT JOIN pagetag ON page.id = pagetag.pageid ) LEFT JOIN tag ON pagetag.tagid = tag.id GROUP BY page.id; 

Not a very pretty query, but should give you what you want – pagetag.id and group_concat(tag.name) will be null for page 4 in the example you’ve posted above, but the page shall appear in the results.