Add condition in where clause

Question

I have 3 tables advert , application and people.

 Select * from advert v, application a 
 inner join people p on p.id = a.id 
 where v.id=a.id

This query returns me all application irrespective of the gender. But sometimes in the advert table, gender is specified as M. So now i want the query above return me only application made by M. To get this value i need to add one more condition, p.gender = v.gender . How do i do this? Sometimes the value of v.gender = n/a . Then I wont need this condition. It should return me all application irrespective gender.

Answer 1

To get your desired results, you need to modify the join condition between advert and people to join the records in either case ( v.gender = 'n/a' or p.gender = v.gender ):

select *
  from advert v
  join application a
    on a.id = v.id
  join people p
    on p.id = a.id
   and (v.gender = 'n/a' or p.gender = v.gender)

Answer 2

I'm a little confused as to what you are asking but here is something to start with. Some example data would also be helpful

select *
from advert v
inner join application a
on a.id  = v.id
inner join people p
on a.id = p.id
where p.gender = 'M';

or

 select *
from advert v
inner join application a
on a.id  = v.id
inner join people p
on a.id = p.id
where p.gender = v.gender;

Answer 3

You could potentially use an IN operator thusly:

WHERE v.GENDER IN ('N/A',p.GENDER)

This would return all records where v.GENDER = 'N/A' or where v.gender = p.GENDER