mysql join and count - mysql

Question

Somehow am not successful with creating the query that I want.
DB is to do with locations, there are the following tables which are relevant
t_location - list of locations incl. field t_location_zipcode, and t_location_id_location
t_zipcodecity - join table just t_zipcodecity_zipcode t_zipcodecity_id_city
t_city - city list with t_city_id_city
t_citystate - join table, t_citystate_id_city, t_citystate_id_state
t_state - list of states with t_state_id_state
Initially I tried to get a list of states with locations using this query:
SELECT DISTINCT `t_state_id_state`
, `t_state_name_full`
FROM (`t_state`)
LEFT JOIN `t_citystate` ON `t_state_id_state` = `t_citystate_id_state`
LEFT JOIN `t_city` ON `t_citystate_id_state` = `t_city_id_city`
LEFT JOIN `t_zipcodecity` ON `t_city_id_city` = `t_zipcodecity_id_city`
LEFT JOIN `t_location` ON `t_zipcodecity_zipcode` = `t_location_zipcode`
ORDER BY `t_state_name_full` asc ­
which works fine.
Now what I also need / want which I am failing dismally at is to get the number of locations in each state. I don't know if it can be done in this one query or if i need another, either way I need help!

Answer 1

you can use a count and a group by. Something like this:
SELECT DISTINCT `t_state_id_state`
, `t_state_name_full`
, COUNT(*)
FROM (`t_state`)
LEFT JOIN `t_citystate` ON `t_state_id_state` = `t_citystate_id_state`
LEFT JOIN `t_city` ON `t_citystate_id_state` = `t_city_id_city`
LEFT JOIN `t_zipcodecity` ON `t_city_id_city` = `t_zipcodecity_id_city`
LEFT JOIN `t_location` ON `t_zipcodecity_zipcode` = `t_location_zipcode`
GROUP BY `t_state_id_state` , `t_state_name_full`
ORDER BY `t_state_name_full` asc

Answer 2

SELECT t_state_id_state
, t_state_name_full
, COUNT(DISTINCT t_location_id_location) AS locations_number
FROM
t_state
LEFT JOIN
t_citystate ON t_state_id_state = t_citystate_id_state
LEFT JOIN
t_city ON t_citystate_id_state = t_city_id_city
LEFT JOIN
t_zipcodecity ON t_city_id_city = t_zipcodecity_id_city
LEFT JOIN
t_location ON t_zipcodecity_zipcode = t_location_zipcode
GROUP BY t_state_id_state
ORDER BY t_state_name_full ASC ­

Answer 3

Ok thats looking good, my bad with the left joins, i was initially trying to get ALL the states which is why i used them. But i change that to use inner joins
SELECT t_state_id_state,
t_state_name_full,
COUNT(DISTINCT t_location_id_location) AS locations_number
FROM t_state
INNER JOIN t_citystate ON t_citystate_id_state = t_state_id_state
INNER JOIN t_city ON t_city_id_city = t_citystate_id_city
INNER JOIN t_zipcodecity ON t_zipcodecity_id_city = t_city_id_city
INNER JOIN t_location ON t_location_zipcode = t_zipcodecity_zipcode
GROUP BY t_state_id_state
ORDER BY t_state_name_full ASC
then i actually end up with a result that looks good !