Question

TABLE1

ID    |     DATE             Ordered
 a    |   10-06-2012    |      1
 b    |   07-07-2012    |      1
 c    |   10-06-2012    |      0

TABLE2

ID    |    OrdersID
 a    |     001
 b    |     002
 c    |     003

TABLE3

OrdersID   |  Items  |  
 001       |   5    |  
 002       |   3    |  
 003       |   7    | 

I have three tables and I would like to search the DATE in TABLE1 e.g. 10-06-2012 and Ordered e.g. 1 and return the ID ‘a’.

In Table2 I would like it to use Table1’s result to get the OrdersID

And in Table3 I would like it to use Tables2’s result to return Items
ID is common in both tables.

Answer 1

Wich RDBMS are you using, MS SQL Server, MySQL, Oracle? Doing some research on how to handle tSQL, create queries, use Joins, etc, will not harm you.

In case you are using MS SQL Server here is a sample of what can be done with the data you provided. Be carefull, nested queries can be awfully slow, check your indexes, primary keys, etc.

--get from Table1 Id's filtering by date and Ordered fields
SELECT t1.Id
  FROM Table1 t1 JOIN Table2 t2
 WHERE t1.[Date] = '10062012 00:00:00'
   AND t1.Ordered = 1

--get from Table2 OrderedID filtered by previous query
SELECT t2.OredersID
  FROM Table2 t2
 WHERE t2.ID IN (SELECT t1.Id
                   FROM Table1 t1 JOIN Table2 t2
                  WHERE t1.[Date] = '10062012 00:00:00'
                    AND t1.Ordered = 1
                 )

--get from Table3 Items filtered by previous query
SELECT t3.Items
  FROM Table3 t3
 WHERE t3.OrdersID IN (SELECT t2.OrdersID
                         FROM Table2 t2
                        WHERE t2.ID IN (SELECT t1.Id
                                          FROM Table1 t1 JOIN Table2 t2
                                         WHERE t1.[Date] = '10062012 00:00:00'
                                           AND t1.Ordered = 1
                                        )
                      )

--Using JOINS, not sure if this is 100% correct
--get from Table3
SELECT t3.Items
  FROM Table3 t3
      JOIN Table2 t2 ON t3.OrdersID = t2.OrdersID
      JOIN Table1 t1 ON t2.ID = t1.ID
 WHERE t1.[Date] = '10062012 00:00:00'
   AND t1.Ordered = 1