Question

This SELECT statement is working just fine but I’d like to be able to repeat it to further refine the search.

SELECT id1 
FROM table1 
WHERE id2 IN (SELECT id 
              FROM table2 
              WHERE name="country" 
                AND value="Mexico")

For instance, if I wanted to find only locations in Mexico that had ‘Beaches’ which would be:

name="features" AND value="Beaches"

…how would I go about paring the results down further with my SELECT statement?

Answer 1

Probably the best way is to execute a new query and just add the additional filtering. It would be possible to filter “manually” in the client application, but that would likely be less efficient for most situations. So run a new query with more restrictions:

SELECT id1 FROM table1 WHERE id2 IN 
        (SELECT id FROM table2 WHERE 
               name="country" AND 
               value="Mexico" AND
               name2 = "features" AND 
               value2 = "Beaches" )

Note that I changed the two new column names to something different (the original query result would not have contained those other values given the original names). If by “refine”, you want to add then perhaps the query should be:

SELECT id1 FROM table1 WHERE id2 IN 
        (SELECT id FROM table2 WHERE 
               ( name="country" AND 
               value="Mexico" ) OR
               ( name = "features" AND 
               value = "Beaches" ))