MySQL sub query with two columns - how to hide the second column? - mysql

Question

I'm having a difficult time wrapping my head around how to do this, even with all the searching and reading I've done on this!
I have a query I am using to try to pull all users from a database that have a zip code that falls within a certain distance of a given decimal coordinate. Here's the query that I am running:
select distinct watch_list.username, enabled
from watch_list, registered_users
where watch_list.username = registered_users.username AND watch_list.watchzip = (
SELECT zip,
( 3959 * acos( cos( radians('29.7632800') ) *
cos( radians( lat ) ) *
cos( radians( lng ) -
radians('-95.3632700') ) +
sin( radians('29.7632800') ) *
sin( radians( lat ) ) ) )
AS distance from zip
HAVING distance <= '10');
There error I get back is expected, as my sub query is returning two columns:
MySQL said: Documentation
#1241 - Operand should contain 1 column(s)
How can I do this and filter on the distance without the sub query returning both columns?
P.S. Just for completion and information sake, the "zip" table contains a list of all zip codes in the U.S. along with their decimal coordinates.

Answer 1

Just move the operation out of the column list:
select distinct watch_list.username, enabled
from watch_list, registered_users
where watch_list.username = registered_users.username
AND watch_list.watchzip = (
SELECT zip
from zip
WHERE ( 3959 * acos( cos( radians('29.7632800') ) *
cos( radians( lat ) ) *
cos( radians( lng ) -
radians('-95.3632700') ) +
sin( radians('29.7632800') ) *
sin( radians( lat ) ) ) ) <= '10');
Edit: As P.Salmon mentions, you probably also want to change AND watch_list.watchzip = to AND watch_list.watchzip IN.