select users have more than one distinct records in mysql

Question

For a table that holds the records of user\'s webpages visiting behavior, how can I select users that visit more than one webpages.

The structure of this tables is:<

Answer 1

just add having clause

SELECT userId, COUNT(DISTINCT webpageId) AS count 
FROM visits 
GROUP BY userId
HAVING COUNT(DISTINCT webpageId) > 1

but if you only what the ID

SELECT userId
FROM visits 
GROUP BY userId
HAVING COUNT(DISTINCT webpageId) > 1

• SQLFiddle Demo

the reason why you are filtering on HAVING clause and not on WHERE is because, WHERE clause cannot support columns that where aggregated.

Answer 2

Try this:

SELECT userId, COUNT(DISTINCT webpageId) AS count FROM visits GROUP BY userId
having COUNT(DISTINCT webpageId) > 1

More: HAVING

Answer 3

While HAVING is a good approach in this case, remember that queries can be nested:

SELECT userId, pageCount
FROM (
    SELECT userId, COUNT(DISTINCT webpageId) AS pageCount
    FROM visits 
    GROUP BY userId) AS n
WHERE pageCount > 1

The actual query plans may differ, especially if HAVING is an optimized case, but there is no reason why the plans must be different. (Compare plans on the specific RDBMS/version if it is an issue or concern.)