SQL query that gives distinct results that match multiple columns

Question

Sorry, I couldn\'t provide a better title for my problem as I am quite new to SQL. I am looking for a SQL query string that solves the below problem.

Let\'s assume t

Answer 1

Select distinct document_id 
from {TABLE} 
where tag in ('tag1','tag2')
group by id 
having count(tag) >=2 

How you generate the list of tags in the where clause depends on your application structure. If you are dynamically generating the query as part of your code then you might simply construct the query as a big dynamically generated string.

We always used stored procedures to query the data. In that case, we pass in the list of tags as an XML document. - a procedure like that might look something like one of these where the input argument would be

   tag1
   tag2



CREATE PROCEDURE [dbo].[GetDocumentIdsByTag]
@tagList xml
AS
BEGIN

declare @tagCount int
select @tagCount = count(distinct *) from @tagList.nodes('tags/tag') R(tags)


SELECT DISTINCT documentid
FROM {TABLE}
JOIN @tagList.nodes('tags/tag') R(tags) ON {TABLE}.tag = tags.value('.','varchar(20)')
group by id 
having count(distict tag) >= @tagCount 

END

OR

CREATE PROCEDURE [dbo].[GetDocumentIdsByTag]
@tagList xml
AS
BEGIN

declare @tagCount int
select @tagCount = count(*) from @tagList.nodes('tags/tag') R(tags)


SELECT DISTINCT documentid
FROM {TABLE}
WHERE tag in
(
SELECT tags.value('.','varchar(20)') 
FROM @tagList.nodes('tags/tag') R(tags)
}
group by id 
having count( distinct tag) >= @tagCount 
END

END