When using a UNION in your Select Statement, you must ensure you use a WHERE statement to return the correct records.

I am using this example.

Select Ordered from Tbl1 where ID=1

The above statement returns all records with ID 1.

Now, let's say we have our table connected to another table to ensure the returned ordered numbers are correct. We could do this.

SELECT Ordered FROM Tbl1 UNION SELECT Ordered FROM Tbl2 where ID = 1

Now, this will return the records for ID=1. However, this will also return records for 2, 3, 4, 5, and so on. However, this code lacks one thing: it does not specify where Tbl1 should get its records.

To retrieve the records for each Query, we need to ensure that a WHERE Clause Is Present at every level.

SELECT Ordered FROM Tbl1 where ID = 1 UNION SELECT Ordered FROM Tbl2 where ID = 1

The above code will now only retrieve records for the ID that matches across both tables.