How to merge two columns into one using c# or sql

Question

Sorry I am really a newbie into programming and I am trying to merge two different columns into one column using sql but if it is not possible can it be done using sql code in c#? I have two tables Product1 and Product2, these tables both have CatID.

For Product1, the CatID contains

1
2
3

For Product2, the CatID contains

1
2
3
4
5

The results that I am getting using union is if they have both similar id it will be merge into one and using concat it will duplicate into like

1 1
2 2
3 3
4
5

But the results that I want is the 1 to 3 is from product1 and then the 4 to 8 from product2 like it will continue on counting with no duplicate:

1
2
3
4
5
6
7
8

Is this possible?

Answer 1

can you try this query, use union

select * from Product1
union
select * from Product2 NOT IN(SELECT CatID FROM Product1)

Answer 2

I am not sure what you want but with LINQ you can create a select. If you show us the SQL code it would be very helpful.

Answer 3

Try it like this:

SELECT CatID, ...OtherColumns...
FROM Product1
UNION SELECT CatID, ...OtherColumns...
FROM Product2
WHERE Product2.CatID NOT IN(SELECT CatID FROM Product1)
ORDER BY CatID

(test here: http://sqlfiddle.com/#!9/7887c ):

CREATE TABLE T1(ID INT, txt VARCHAR(10));
INSERT INTO T1 SELECT 1, 'test A'
        UNION  SELECT 2, 'test B'
        UNION  SELECT 3, 'test C';

CREATE TABLE T2(ID INT, txt VARCHAR(10));
INSERT INTO T2 SELECT 1, 'test 1'
        UNION  SELECT 2, 'test 2'
        UNION  SELECT 3, 'test 3' 
        UNION  SELECT 4, 'test 4'        
        UNION  SELECT 5, 'test 5';

SELECT ID, txt
FROM T1
UNION SELECT ID, txt
FROM T2
WHERE T2.ID NOT IN(SELECT ID FROM T1)
ORDER BY ID

The result:

ID  txt
1   test A
2   test B
3   test C
4   test 4
5   test 5