Question

I already looked up many posts about this problem (subqueries being very slow in sqlite). but I’m not really good with sql and i don’t know what i can do.

i have this query:

SELECT * FROM data d WHERE d.category = 3 AND 
(SELECT COUNT(id) FROM data_tag WHERE data = d.id AND (tag = 2136 OR tag = 8)) >= 2 
ORDER BY id ASC

i have 3 tables
data,tag and data_tag (n-m of data and tag)
every data has n tags and in this query i search datas by tags (2 tags, both must be in data)

i switched my database from SQL Server to sqlite and besides this query everything works fine.
in SQL Server this one took less then 1 sec to execute and in sqlite it takes about 1min.
plz give me some tips.

Answer 1

SELECT d.* FROM data d
INNER JOIN data_tag ON data_tag.data = d.id AND (tag = 2136 OR tag = 8)
WHERE d.category = 3 
GROUP BY d.id
HAVING COUNT(data_tag.id) >= 2 
ORDER BY id ASC