mysql - SQL error say column from COUNT does not exisit -


this question has answer here:

select c.review, m.category, u.username, i.item, i.item_id, m.cat_id, count(rv.review_id) totalcount reviews c left join review_vote rv    on c.review_id = rv.review_id left join users u    on u.user_id = c.user_id  left join items    on i.item_id = c.item_id left join master_cat m    on m.cat_id = i.cat_id length(c.review) > 50 , m.category = 'movies' , totalcount > 2 group rv.review_id order rand() limit 1

i error:

#1054 - unknown column 'totalcount' in 'where clause'

i selecting column right away, how come doesn't exist?

i trying random select review listed (or voted on 2 or more times) in in table rv. not sure if using group by correctly?

with aggregate columns (like count()), must use having clause place condition on them:

select c.review, m.category, u.username, i.item, i.item_id, m.cat_id, count(rv.review_id) totalcount reviews c left join review_vote rv    on c.review_id = rv.review_id left join users u    on u.user_id = c.user_id  left join items    on i.item_id = c.item_id left join master_cat m    on m.cat_id = i.cat_id length(c.review) > 50 , m.category = 'movies' group rv.review_id having count(rv.review_id) > 2 -- added line! order rand() limit 1

some databases (including mysql) allow use column alias, eg having totalcount > 2, using expression works databases. ie mysql (at least), code as:

.... group rv.review_id having totalcouunt > 2 ...

but wouldn't portable other databases.


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