SQL SERVER merge two column, combine it, and count the same - asp.net

Question

I want to create a barcode by merge and combine two column.
here is my table :
ID | Items1 | Items2 | BArcode
001 | Shirt | CPU |
002 | Shirt | CPU |
001 | Shoes | Monitor |
002 | Jacket | Monitor |
001 | Shoes | CPU |
002 | | Keyboard |
002 | | Keyboard |
001 | Shirt | Keyboard |
002 | Shirt | |
The barcode created based on ID+Item1/Items2+Count. The count get from counting how many times one ID have oredered the same item. I want it to display only the data that haven't generated a barcode, so it's when the Barcode column value is null, from the above table the Barcode is null:
ID | Barcode |
001 | 001Shirt1 |
002 | 002Shirt1 |
001 | 001Shoes1 |
002 | 002Jacket1 |
001 | 001Shoes2 |
001 | 001Shirt2 |
002 | 002Shirt2 |
001 | 001CPU1 |
002 | 002CPU1 |
001 | 001Monitor1 |
002 | 002Monitor1 |
001 | 001CPU2 |
002 | 002Keyboard1 |
002 | 002Keyboard2 |
001 | 001Keyboard1 |
here is my first code :
Dim strcommand As String = "select [ID], ([ID] + [Items1])
as Barcode from tbl_Request where [Items1] != 'null'
and Barcode = 'null' union select ([ID] + [Items2])
from tbl_Request where [Items2] != 'Null' and Barcode = 'null'"
it doesn't work. it say "All queries combined using a UNION, INTERSECT or EXCEPT operator must have an equal number of expressions in their target lists". on my code above I haven't implement the counting yet. does anyone know how to do it?
Thanks in advances....

Answer 1

You can use this query to generate the barcode values:
;with cte as
(select id, item1 item, row_number() over (partition by id, item1 order by getdate()) rn
from items
where item1 is not null and barcode is null
union
select id, item2 item, row_number() over (partition by id, item2 order by getdate()) rn
from items
where item2 is not null and barcode is null)
select id, cast(id as varchar) + item + cast(rn as varchar) barcode
from cte
If you wanted to add this to a new table, say tbl_barcode with columns id and barcode, you would do this:
;with cte as
(select id, item1 item, row_number() over (partition by id, item1 order by getdate()) rn
from items
where item1 is not null and barcode is null
union
select id, item2 item, row_number() over (partition by id, item2 order by getdate()) rn
from items
where item2 is not null and barcode is null)
insert into tbl_barcode (id, barcode)
select id, cast(id as varchar) + item + cast(rn as varchar) barcode
from cte

Answer 2

The error that you are getting is that the union join that you have created does not contain the same fields in the second select statement, as your original select statement. SQL UNION Operator, Notice that each SELECT statement within the UNION must have the same number of columns.
So therefore you will need to change
select ([ID] + [Items2])
to
select [ID], ([ID] + [Items2])

Answer 3

declare #x table (ID varchar(20),Items1 VARCHAR(10),Items2 VARCHAR(10),BARCODE INT)
INSERT INTO #x
(ID,Items1,Items2,BARCODE)
VALUES ('001','Shirt','CPU',NULL)
INSERT INTO #x
(ID,Items1,Items2,BARCODE)
VALUES ('001',NULL,'Monitor',NULL)
INSERT INTO #x
(ID,Items1,Items2,BARCODE)
VALUES ('002','TRouser','Monitor',NULL)
select ID,
Case when Items1 IS NOT NULL Then ID +Items1+
CAST(DENSE_RANK()OVER(PARTITION by Items1 order by Items1 desc)AS VARCHAR)
when Items2 IS NOT NULL Then ID +Items2+
CAST(DENSE_RANK()OVER(PARTITION by Items2 order by Items1 desc)AS VARCHAR)
ELSE '' END AS Barcode from #x