SQL issue - how do I select all tuples which contain all references in a second table?
Heres the deal - I have three tables here:
Companies:
ID | NAME | DETAILS
TAGS
ID | TAGNAME
TAGS_COMPANIES
COMPANY_ID | TAGID
Using a nest开发者_JS百科ed query I can retrieve all companies that are tagged by tags in a certain set i.e:
select c.* from companies c where c.id in (select t.company_id where t.tagid in (12,43,67))
The above query returns all companies that have an either tag id 12, 43 or 67 but I need to retrieve all companies who are tagged 12 AND 43 AND 67
How would I redo my query here? I'm using MySQL
Not too efficient but works:
select c.*
from companies c
where c.id in (select t.company_id from tags_companies t where t.tagid = 12)
and c.id in (select t.company_id from tags_companies t where t.tagid = 43)
and c.id in (select t.company_id from tags_companies t where t.tagid = 67)
Another possibility using a HAVING clause:
select c.id, c.name, c.details
from companies c join tags_companies t on c.id = t.company_id
where t.tagid in (12, 43, 67)
group by c.id, c.name, c.details
having count(distinct t.tagid) = 3
With one subquery.
select c.*
from companies c
where (c.id, 3) in
(select t.company_id, count(distinct t.tagid)
from tags t
where t.tagid in (12,43,67)
group by t.company_id)
magic number 3 means different tags count.
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