Question

I have following table structures:

 Item:
 -----------------------
 item_id INT (PRIMARY),
 category_id MEDIUMINT,
 name VARCHAR(40)

 reservation:
 -----------------------
 id INT (PRIMARY),
 item_id INT,
 date DATE,
 slot VARCHAR(50)

i want all rows of a particular category_id from table Item with a join to reservation table ON column item_id WHERE reservation.date = ‘something’ to be returned in a query. There is no guarantee that reservation row will be available with the queried date. But i need all the rows of corresponding category_id to be returned from Item table even if reservation row is absent. How can this be achived?

regards,
ravi.

Answer 1

Sounds like a left join would fit the bill. If you add the date restriction to the on clause, the date restriction will not filter out rows from Item.

select  *
from    Item i
left join
        reservation r
on      i.item_id = r.item_id
        and r.date = '2012-06-11'
where   category_id = 42