I have 5 mysql tables as described below. clinics table
id
name
d_location_subscription table
id
clinic_id
t_id //t_id will contain a foreign key of d_cities, d_states or d_countries table
type "country" "state" "city"
d_countries table
id
name
code
d_states table
id
d_country_id
name
code
d_city table
id
d_state_id
name
code
d_location_subscription table is used to record clinic's subscription for a location(it may be a city, state or country). I'm expecting to get all subscribed cities for a specific clinic using d_location_subscription table.
For example, if clinic A is subscribed to Texas state, I should be able to get all city ids for clinic A.
I created following sql query, it looks ugly but generate a close result what i want to achieve.
select
`d`.`id` AS `clinic_id`,
if((`dct`.`id` is not null),`dct`.`id`,if((`dct1`.`id` is not null),`dct1`.`id`,`dct2`.`id`)) AS `d_city_id`
from ((((((((
`d_location_subscriptions` `dls`
join `clinics` `d`
on((`d`.`id` = `dls`.`clinic_id`)))
left join `d_countries` `dc`
on(((`dc`.`id` = `dls`.`t_id`) and (`dls`.`type` = 'country'))))
left join `d_states` `ds`
on((`ds`.`d_country_id` = `dc`.`id`)))
left join `d_cities` `dct2`
on((`dct2`.`d_state_id` = `ds`.`id`)))
left join `d_states` `ds1`
on(((`ds1`.`id` = `dls`.`t_id`) and (`dls`.`type` = 'state'))))
left join `d_cities` `dct`
on((`dct`.`d_state_id` = `ds1`.`id`)))
left join `d_cities` `dct1`
on(((`dct1`.`id` = `dls`.`t_id`) and (`dls`.`type` = 'city'))))
)
when there is record with type "country" in d_location_subscription table, I receive following result. total number of records returned are equal to the number of d_states table records.
How should I get rid of those Null values by changing above query? And please advice me if this is the correct way to acheive similar functionality. Thanks in advance :)