Creating query that returns id if condition is matched in rows from two tables

Question

I\'m learning SQL/dbms and using Postgres. I want to return rows that both have a certain value in a certain column. For example in tables Carpets and Curtain

Answer 1

These both query will give you result which you want....

SELECT Carperts.id
  FROM Carpets INNER JOIN Curtains ON Carpets.colour = Curtains.colour
  and colour = 'light yellow';


SELECT Carperts.id
  FROM Carpets INNER JOIN Curtains ON Carpets.colour = Curtains.colour
  WHERE colour = 'light yellow';