SQL - Get AVG from count from another table -


so have 2 tables: listing , reviews. try listing best reviews, based in state. need avg reviews listing , desc listings.

table structure: listing: id; title; state; ...

reviews: id; listing_id; rating (from 1-5)

i solve desc listing of reviews try avg of rating of reviews.

select *,        (select count(*)            reviews rv           ls.id = rv.listing_id) count    listing ls   ls.state ='$get_state'   order count desc

sample data:

listing:  id title                state  1  hotel nice view arizona 2  hotel stay        arizona  review:  id listing_id rating 1  1          4(stars) 2  1          4(stars) 3  1          3(stars) 4  2          5(stars)

listing id 1 got 3 reviews , total star value of 11 / 3 reviews = 3.6 stars

listing id 2 got 1 review , total star value of 5 / 1 = 5 stars

now should first listing 2 , listing 1 want display whole thing on php page.

what can next? help

you can use avg() function average rating

select ls.id,        title,        state,        round(avg(rating),2) avg_rating   listing ls   join review rv     on ls.id = rv.listing_id  ls.state = '$get_state'  group ls.id,           title,           state  order avg_rating desc

if using mssql, cast column rating decimal precision (as float or decimal)

round(avg(cast(rating float)),2) avg_rating

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