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declare @userId bigint;

DECLARE my_cursor CURSOR FOR
select userId from users where userdetailId is NULL;

OPEN my_cursor
FETCH NEXT FROM my_cursor INTO @userId

WHILE @@FETCH_STATUS = 0
BEGIN
	insert into UserDetail DEFAULT VALUES;
	update Users set UserDetailId = (SELECT SCOPE_IDENTITY()) where UserId = @userId;
	FETCH NEXT FROM my_cursor INTO @userId
END

CLOSE my_cursor
DEALLOCATE my_cursor
GO