Find missing rows for a column in the same table - sql-server

Question

I need to find the missing rows that exist in a table of our SQL Server. I have a list of 3 items, for example, that must always exist for each header_id as individual rows with the appropriate product_id.
So ideally the data should be appear as this:
header_id product_id product_group_id
10 Main Product 7
10 Bundle Item 1 50
10 Bundle Item 2 50
10 Bundle Item 3 50
However, due to the process in which the information is added to the database it requires each line to be added individually by the data entry person. As a result we are seeing values such as this where "Bundle Item 2" is missing:
header_id product_id product_group_id
10 Main Product 7
10 Bundle Item 1 50
10 Bundle Item 3 50
The following script displays the header_id's that are missing a missing product_id however it only provides the product_id of "Main Product".
SELECT header_id, product_id, product_group_id
FROM Table1
WHERE
(product_id = 'Main Product')
AND (header_id NOT IN (SELECT product_id
FROM table1 AS table1_1
WHERE (product_id = 'Bundle Item 2')))
I know I can use unions to group multiple queries and force a description value such as this below but would prefer an alternative way if possible.
SELECT header_id, product_id, product_group_id, 'Bundle Item 2' as Description
FROM Table1
WHERE
(product_id = 'Main Product')
AND (header_id NOT IN (SELECT product_id
FROM table1 AS table1_1
WHERE (product_id = 'Bundle Item 2')))
UNION
SELECT header_id, product_id, product_group_id, 'Bundle Item 3' as Description
FROM Table1
WHERE
(product_id = 'Main Product')
AND (header_id NOT IN (SELECT product_id
FROM table1 AS table1_1
WHERE (product_id = 'Bundle Item 3')))

Answer 1

yup,you hv to redesign your DB.There can be so many data namely anything.how do i know under which main product id comes what all sub product id.and if anything is missing .I cannot hard code 'Bundle Item 2'.
If each main product will have at least 3 sub product then using row_number you can find...what ?
Declare #t table (header_id int,product_id varchar(50),product_group_id int)
insert into #t
select 10, 'Main Product', 7 union all
select 10, 'Bundle Item 1' , 50 union all
select 10, 'Bundle Item 2' , 50 union all
select 10, 'Bundle Item 3' , 50
select *,row_number()over(order by product_id)rn from #t where product_group_id<>7

Answer 2

If you know you need exactly those four products, then you can handle this by creating all possible combinations of header_id and product. Then use left outer join to find the ones that are missing:
with prods as (
select 'Main Product' as product union all
select 'Bundle Item 1' union all
select 'Bundle Item 2' union all
select 'Bundle Item 3'
),
allheaderprods as (
select distinct header_id, product
from prods cross join
table1
)
select ahp.*
from allheaderprocs ahp left outer join
header h
on ahp.header_id = h.header_id and
ahp.product = h.product
where ahp.header_id is null;