how to update foreign key - sql-server

Question

I have 2 tables; design of first table is like below:
Table 1:
id_Doc_line_sheet (pk),Autonumber
DocNo (text)
lineNo (text)
Sheet No (text)
Combination of fields (DocNo, lineNo, Sheet No) is index and unique.
Design of second table is like below:
Table 2:
id_Doc_line_trans (pk), Autonumber
id_Doc_line_sheet (fk),Number
name
Now in table1, for the field lineNo I have records with leading spaces and without leading spaces like below:
id_Doc_line_sheet DocNo lineNo Sheet No
------------------------------------------------------------------
1001 doc-0001 line-0001 1
1002 doc-0001 line-0001 1
1003 doc-0001 line-0001 2
1004 doc-0001 line-0001 2
1005 doc-0002 line-0002 1
1006 doc-0002 line-0002 1
1007 doc-0001 line-0005 1
1008 doc-0001 line-0005 1
And I want deleted these records with leading spaces but at first I want to update (id_Doc_line_sheet) for each unique (DocNo,lineNo,Sheetno) to correct one (without leading space).
I mean if the table2 is like below:
id_Doc_line_trans id_Doc_line_sheet name
---------------------------------------------------
1 1001 name01
2 1002 name02
3 1003 name03
4 1004 name04
5 1007 name07
6 1008 name08
I update (id_Doc_line_sheet) to something like below:
id_Doc_line_trans id_Doc_line_sheet name
---------------------------------------------------
1 1001 name01
2 1001 name02
3 1003 name03
4 1003 name04
5 1007 name07
6 1007 name08
And then delete records with leading spaces from first table.
Please help how I can do it?

Answer 1

Based on what I understood, it seems you want to update the table2 based on the sheet_no first id used. If so, you can use the following:
Explanation
You need to get the first record in table1 based on the sheet_no using report cte
Find the corresponding sheet_no for each row in table2
Update the table2 entries where row_number =1
Query
;with report as(
select row_number() over(partition by sheet_no order by id_doc_line_sheet) as [Row],id_doc_line_sheet,sheet_no
from table1
where line_no not like ' %' -- here you can ensure that lin_no doesn't start with leading space
), combined as(
select t2.id_doc_line_trans,
t2.id_doc_line_sheet,
t1.sheet_no
from table2 t2
inner join table1 t1 on t2.id_doc_line_sheet = t1.id_doc_line_sheet
)
update t set t.id_doc_line_sheet = r.id_doc_line_sheet
from report r
inner join combined c on r.sheet_no = c.sheet_no
inner join table2 t on t.id_doc_line_trans = c.id_doc_line_trans
where r.[Row]=1
result after updating table2
id_doc_line_trans id_doc_line_sheet name
1 1001 name01
2 1001 name02
3 1003 name03
4 1003 name04
Then you can apply the delete statement based on your requirements
Here a working demo
Hope this will help you

Answer 2

Here is an approach which does not use analytic functions, which was the easiest way to approach this in my mind. We can aggregate over table1 and pivot out both the id of the records both with and without leading whitespace. Also, we can check to make sure a given document/sheet even has such a page occurring. Then, all we need to do is join table2 to this first CTE to get the old and new id values in a single record.
WITH cte1 AS (
SELECT
DocNo, [Sheet No],
MAX(CASE WHEN [lineNo] LIKE ' %' THEN id_Doc_line_sheet END) AS id_old,
MAX(CASE WHEN [lineNo] NOT LIKE ' %' THEN id_Doc_line_sheet END) AS id_new
FROM table1
GROUP BY DocNo, [Sheet No]
HAVING SUM(CASE WHEN [lineNo] LIKE ' %' THEN 1 ELSE 0 END) > 0
),
cte2 AS (
SELECT
t1.id_Doc_line_trans, t1.id_Doc_line_sheet, t1.name, t2.id_old, t2.id_new
FROM table2 t1
INNER JOIN cte1 t2
ON t1.id_Doc_line_sheet = t2.id_old
)
UPDATE cte2
SET id_Doc_line_sheet = id_new;
Note that the update logic is trivial; all the information and records of interest were already included in the second CTE.
Demo