Joining 3 tables based on common columns - sql-server

Question

I have four tables - tblBase, tblLookup, tblData and tblData2
tblBase
+---------+----------+-----------+------------+
| Base_ID | Base_Num | Base_Type | Base_Date |
+---------+----------+-----------+------------+
| 1 | 1234 | ABC | 01/05/2016 |
| 2 | 3456 | DEF | 02/05/2016 |
| 3 | 7890 | GHI | 03/05/2016 |
+---------+----------+-----------+------------+
tblLookup
+-----------+-------------+
| Lookup_ID | Lookup_Name |
+-----------+-------------+
| 1 | Apple |
| 2 | Orange |
| 3 | Banana |
+-----------+-------------+
tblData
+-----------+----------+------------+
| Data_Name | Data_Num | Data_Date |
+-----------+----------+------------+
| Apple | 1234 | 02/05/2016 |
| Orange | 3456 | 03/05/2016 |
| Guava | 5937 | 04/05/2016 |
+-----------+----------+------------+
tblData2
+------------+-----------+------------+
| Data2_Name | Data2_Num | Data2_Date |
+------------+-----------+------------+
| Grapes | 3953 | 02/05/2016 |
| Orange | 3456 | 03/05/2016 |
| Banana | 7890 | 04/05/2016 |
| Banana | 1473 | 07/05/2016 |
+------------+-----------+------------+
I am trying to get the Data_Date from tblData or tblData2 (where ever the data exists) join with tblBase where Base_Num matches . As the common columns exists in tblLookup, I need to join all the four tables.
For example, Base_ID = 3, Base_Num = 7890, should pick up Data_Date from tblData2, as both Base_ID (Banana) and Base_Num (7890) matches.
I tried doing INNER JOIN however it did not give the desired result.
I'm looking for a resulting table like this:
+---------+----------+-----------+------------+-------------------+
| Base_ID | Base_Num | Base_Type | Base_Date | Desired_Data_Date |
+---------+----------+-----------+------------+-------------------+
| 1 | 1234 | ABC | 01/05/2016 | 02/05/2016 |
| 2 | 3456 | DEF | 02/05/2016 | 03/05/2016 |
| 3 | 7890 | GHI | 03/05/2016 | 04/05/2016 |
+---------+----------+-----------+------------+-------------------+

Answer 1

You may try Left Join
SELECT B.Base_ID, B.Base_Num , B.Base_Type, B.Base_Date,
D1.Data_Name AS Data1, D1.Data_Date AS DESIRED_DATE1
D2.Data2_Name AS Data2, D2.Data2_Date AS DESIRED_
FROM tblBase B
JOIN tblLookup L ON L.Lookup_ID=B.Base_ID
LEFT JOIN tblData D1 ON D1.Data_Num = B.Base_Num
LEFT JOIN tblData2 D2 ON D2.Data2_Num = B.Base_Num
WHERE <Condition>

Answer 2

declare #tblbase table (Base_ID int, Base_Num int, Base_Type varchar(3), Base_Date varchar(10))
Insert into #tblbase
values
( 1 , 1234 , 'ABC', '01/05/2016'),
( 2 , 3456 , 'DEF', '02/05/2016'),
( 3 , 7890 , 'GHI', '03/05/2016')
declare #tblLookup table (Lookup_ID int, Lookup_Name varchar(10))
insert into #tblLookup
values
( 1 , 'Apple' ),
( 2 , 'Orange'),
( 3 , 'Banana')
declare #tbldata table (Data_Name varchar(10), Data_Num int, Data_Date varchar(10))
Insert into #tbldata
values
( 'Apple' , 1234 , '02/05/2016'),
( 'Orange' , 3456 , '03/05/2016'),
( 'Guava' , 5937 , '04/05/2016')
declare #tbldata2 table (Data_Name varchar(10), Data_Num int, Data_Date varchar(10))
Insert into #tbldata2
values
( 'Grapes', 3953 , '02/05/2016'),
( 'Orange' , 3456 , '03/05/2016'),
( 'Banana' , 7890 , '04/05/2016'),
( 'Banana' , 1473 , '07/05/2016')
/*
Expected result
+---------+----------+-----------+------------+-------------------+
| Base_ID | Base_Num | Base_Type | Base_Date | Desired_Data_Date |
+---------+----------+-----------+------------+-------------------+
| 1 | 1234 | ABC | 01/05/2016 | 02/05/2016 |
| 2 | 3456 | DEF | 02/05/2016 | 03/05/2016 |
| 3 | 7890 | GHI | 03/05/2016 | 04/05/2016 |
+---------+----------+-----------+------------+-------------------+
*/
select bt.*,u.data_date as Desired_data_date
from #tblbase bt
join #tblLookup lu on lu.lookup_id = bt.base_id
join
(select t1.* from #tbldata t1
union
select t2.* from #tbldata2 t2
) u
on u.data_name = lu.Lookup_Name
where u.Data_Num = bt.Base_Num
order by bt.Base_Date