MySql Query: Select top 3 rows from table for each category
I have a table with records and it has a row called category
. I have inserted too many articles and I want to select only two articles from each category.
I tried to do something like this:
I created a view:
CREATE VIEW limitrows AS
SELECT * FROM tbl_artikujt ORDER BY articleid DESC LIMIT 2
Then I created this query:
SELECT *
FROM tbl_artikujt
WHERE
artikullid IN
(
SELECT artikullid
FROM limitrows
ORDER BY category DESC
)
ORDER BY category DESC;
But this is not working and is giving me only two records?
LIMIT only stops the number of results the statement returns. What you're looking for is generally called analytic/windowing/ranking functions - which MySQL doesn't support but you can emulate using variables:
SELECT x.*
FROM (SELECT t.*,
CASE
WHEN @category != t.category THEN @rownum := 1
ELSE @rownum := @rownum + 1
END AS rank,
@category := t.category AS var_category
FROM TBL_ARTIKUJT t
JOIN (SELECT @rownum := NULL, @category := '') r
ORDER BY t.category) x
WHERE x.rank <= 3
If you don't change SELECT x.*
, the result set will include the rank
and var_category
values - you'll have to specify the columns you really want if this isn't the case.