Opposite of inner join

Question

What will be the opposite of inner join? For a table table Person (int PersonId, varchar PersoName, int AddrId), I want to know the rows in Person with bad Ad

Answer 1

If you consider an inner join as the rows of two tables that meet a certain condition, then the opposite would be the rows in either table that don't.

For example the following would select all people with addresses in the address table:

SELECT p.PersonName, a.Address
FROM people p
JOIN addresses a
    ON p.addressId = a.addressId

I imagine the "opposite" of this would be to select all of the people without addresses and all addresses without people. However this doesn't seem to be what you are asking, you seem to be interested in just one component of this: all the people without an address in the addresses table.

For this a left join would be best:

SELECT p.PersonName
FROM people p
LEFT JOIN addresses a
   ON p.addressId = a.addressId
WHERE a.addressId IS NULL

Note that often some prefer to write it differently as in their opinion it is more readable (however in my experience with large tables it performs worse than the above way):

SELECT PersonName
FROM people
WHERE addressId NOT IN (SELECT addressId FROM addresses)