根据MySQL中第一个表的结果选择第二个表中的项目

Question

I have two MySQL tables tableA and tableB. In tableA I want to select all zip codes and their respective coordinates using the following query:

SELECT zip,lat,lng
FROM tableA

However, I want to create a one to many relationship and select all items in a second table based on the results from the first table. For example I want to select a list of all locations in tableB that are in each zip code in tableA. Normally I would try to run a query like the following (assuming the zip code is '00000':

SELECT locations
FROM tableB
WHERE distanceFormula(tableA.lat,tableA.lng,tableB.lat,tableB.lng) < 50

How can I combine these two queries to run the second query for every result in the first query.

Answer 1

Hopefully you should be able to do something like the following:

SELECT A.`zip`, A.`lat`, A.`lng`, B.`location`
FROM `tableA` AS A
CROSS JOIN (
    SELECT *
    FROM `tableB` AS B
    WHERE distanceFormula( A.`lat`, A.`lng`, B.`lat`, B.`lng` ) < 50
) AS B
WHERE A.`zip` = '000000';

My syntax might be slightly incorrect as I haven't done joins like this in MySQL before (I've only done them on MSSQL)

Answer 2

You can use subquerys:

SELECT locations
FROM tableB
WHERE zip IN 
(SELECT zip
FROM tableA);

http://www.mysqltutorial.org/mysql-subquery/