What is wrong with this database query?
- by outsyncof
I have the following tables in a database (i'll only list the important attributes):
Person(ssn,countryofbirth)
Parents(ssn,fatherbirthcountry)
Employment(ssn, companyID)
Company(companyID, name)
My task is this: given fatherbirthcountry as input, output the names of companies where persons work whose countryofbirth match the fatherbirthcountry input.
I pretend that the fatherbirthcountry is Mexico and do this:
SELECT name
FROM Company
WHERE companyid = (SELECT companyid
FROM Employment
WHERE ssn = (SELECT ssn
FROM Person
WHERE countryofbirth = 'Mexico');
but it is giving me an error:
>Scalar subquery is only allowed to return a single row.
am I completely off track? Can anybody please help?
