Question

Hi were trying to perform a mysql select which isnt going to plan and hoping someone can shed some light on it.

we have estimated 10,000 plus listing records, a customer can have several listing records for different locations. we need to select all customer listings where at least one of the locations is equal to a specifield location.

so for example lets say customer 1 has a listing in sheffiled, doncaster, leeds, wakefield and customer 2 has listings in london and brighton.

Now I want to select all customer listings where one of the listings is for the area sheffield.

Id hope to get back the 4 rows for customer 1 because one of his listings is in sheffield.

for the sake of this example lets just presume the table consists of just customerId and LocationName

I need to select all customerIds where one of the locationNames = sheffield. So Id get 4 rows retruend with the cusotmer ID and the 4 locations

How do you write this query in mysql? Im guessing subselect but not too sure.

Answer 1

SELECT customerid FROM customers_location
WHERE customerid IN(SELECT DISTINCT customerid FROM customers_location WHERE LocationName = 'sheffield')