T-SQL Match records 1 to 1 without join condition - sql

Question

I have a group of enitities which need to have another record associated with them from another table.
When I try to output an Id for the table to be matched on it doesn't work because you can only output from inserted, updated etc.
DECLARE #SignatureGlobalIdsTbl table (ID int,
CompanyBankAccountId int);
INSERT INTO GlobalIds (TypeId)
-- I Cannot output cba.Id into the table since its not from inserted
OUTPUT Inserted.Id,
cba.Id
INTO #SignatureGlobalIdsTbl (ID,
CompanyBankAccountId)
SELECT (#DocumentsGlobalTypeKey)
FROM CompanyBankAccounts cba
INNER JOIN Companies c ON c.CompanyId = cba.CompanyId
WHERE SignatureDocumentId IS NULL
AND (SignatureFile IS NOT NULL
AND SignatureFile != '');
INSERT INTO Documents (DocumentPath,
DocumentType,
DocumentIsExternal,
OwnerGlobalId,
OwnerGlobalTypeID,
DocumentName,
Extension,
GlobalId)
SELECT SignatureFile,
#SignatureDocumentTypeKey,
1,
CompanyGlobalId,
#OwnerGlobalTypeKey,
[dbo].[fnGetFileNameWithoutExtension](SignatureFile),
[dbo].[fnGetFileExtension](SignatureFile),
documentGlobalId
FROM (SELECT c.GlobalId AS CompanyGlobalId,
cba.*,
s.ID AS documentGlobalId
FROM CompanyBankAccounts cba
INNER JOIN Companies c ON c.CompanyId = cba.CompanyId
CROSS JOIN #SignatureGlobalIdsTbl s) info
WHERE SignatureDocumentId IS NULL
AND (SignatureFile IS NOT NULL
AND SignatureFile != '');
I Tried to use cross join to prevent cartesian production but that did not work. I also tried to output the rownumber over some value but I could not get that to be stored in the table either.
If I have two seperate queries which return the same amount of records, how can I pair the records together without creating cartesian production?

Answer 1

'When I try to output an Id for the table ... it doesn't work.'
This seems to be because one of the columns you want to OUTPUT is not actually part of the insert. It's an annoying problem and I wish SQL Server would allow us to do it.
Someone may have a much better answer for this than I do, but the way I usually approach this is
Create a temporary table/etc of the data I want to insert, with a column for ID (starts blank)
Do an insert of the correct amount of rows, and get the IDs out into another temporary table,
Assign the IDs as appropriate within the original temporary table
Go back and update the inserted rows with any additional data needed (though that's probably not needed here given you're just inserting a constant)
What this does is to flag/get the IDs ready for you to use, then you allocate them to your data as needed, then fill in the table with the data. It's relatively simple although it does do 2 table hits rather than 1.
Also consider doing it all within a transaction to keep the data consistent (though also probably not needed here).
How can I pair the records together?
A cross join unfortunately multiplies the rows (number of rows on left times the number of rows on the right). It is useful in some instances, but possibly not here.
I suggest when you do your inserts above, you get an identifier (e.g., companyID) in your temp table and join on that.
If you don't have a matching record and just want to assign them in order, you can use an answer similar to my answer in another recent question How to update multiple rows in a temp table with multiple values from another table using only one ID common between them?
Further notes
I suggest avoiding table variables (e.g., DECLARE #yourtable TABLE) and use temporary tables (CREATE TABLE #yourtable) instead - for performance reasons. If it's only a small amount of rows it's OK, but it gets worse as it gets larger as SQL Server assumed that table variables only have 1 row
In your bottom statement, why is there the SELECT statement in the FROM clause? Couldn't you just get rid of that select statement and have the FROM clause list the tables you want?

Answer 2

I figured out a way to have access to the output, by using a merge statement.
DECLARE #LogoGlobalIdsTbl TABLE (ID INT, companyBankAccountID INT)
MERGE GlobalIds
USING
(
SELECT (cba.CompanyBankAccountId)
FROM CompanyBankAccounts cba
INNER JOIN Companies c on c.CompanyId = cba.CompanyId
WHERE cba.LogoDocumentId IS NULL AND (cba.LogoFile IS NOT NUll AND cba.LogoFile != '')
) src ON (1=0)
WHEN NOT MATCHED
THEN INSERT ( TypeId )
VALUES (#DocumentsGlobalTypeKey)
OUTPUT [INSERTED].[Id], src.CompanyBankAccountId
INTO #LogoGlobalIdsTbl;