Virtual column unknown when comparing lat lng - mysql

Question

I am attempting to return only rows where the latitude and longitude being passed into the query, when compared to the latitude and longitude stored in the database, is a certain amount of miles apart.
The query is as follows:
SELECT
c.google_theatre_id
AS cinema_id,
c.name
AS cinema_name,
( 3959 * acos( cos( radians('50.4521013') ) *
cos( radians( latitude ) ) *
cos( radians( longitude ) -
radians('-3.5247389') ) +
sin( radians('50.4521013') ) *
sin( radians( latitude ) ) ) )
AS distance
FROM
google_cinemas c, app_users u
WHERE
distance < u.range
AND
u.id = 126
ORDER BY
distance
The query is designed to get the distance and then compare it to a column (range) in the app_users table.
When running the query, I'm getting an error of distance being an unknown column.
As this is a virtual column, is there a different way of comparing?
Thanks :)

Answer 1

you need to use HAVING instead of WHERE.. think of it this way WHERE is when you make an order at a restraunt and HAVING is picking stuff off of the plate when it comes to your table... you cannot reference an alias before the plate comes to your table only after it has been built
SELECT
c.google_theatre_id AS cinema_id,
c.name AS cinema_name,
( 3959 * acos( cos( radians('50.4521013') ) *
cos( radians( latitude ) ) *
cos( radians( longitude ) -
radians('-3.5247389') ) +
sin( radians('50.4521013') ) *
sin( radians( latitude ) ) )
) AS distance
FROM google_cinemas c, app_users u
WHERE u.id = 126
HAVING distance < u.range
ORDER BY distance
alternatively you can use it as a sub query which could be faster since HAVING re-evaluates the entire query.
SELECT *
FROM
( SELECT
c.google_theatre_id AS cinema_id,
c.name AS cinema_name,
( 3959 * acos( cos( radians('50.4521013') ) *
cos( radians( latitude ) ) *
cos( radians( longitude ) -
radians('-3.5247389') ) +
sin( radians('50.4521013') ) *
sin( radians( latitude ) ) )
) AS distance,
u.range
FROM google_cinemas c, app_users u
WHERE u.id = 126
ORDER BY distance
)t
WHERE distance < range