Question

Can anyone suggest me how to compare two database tables in sql server and return the rows in the second table which are not in the first table. The primary key in both the tables is not the same. For instance, the tables are as follows.

Table1

ID             Name               DoB
1              John Doe           20/03/2012
2              Joe Bloggs         31/12/2011

Table2

ID             Name                DoB
11             John Doe            20/03/2012
21             Joe Bloggs          31/12/2011
31             James Anderson      14/04/2010

The sql query should compare only the Name and DoB in both tables and return
31 James Anderson 14/04/2010

Thanks.

Answer 1

Pretty simple, use a LEFT OUTER JOIN to return everything from Table2 even if there isn’t a match in Table1, then limit that down to only rows that don’t have a match:

SELECT Table2.ID, Table2.Name, Table2.DoB
FROM Table2
LEFT OUTER JOIN Table1 ON Table2.Name = Table1.Name AND Table2.DoB = Table1.DoB
WHERE Table1.ID IS NULL