Copy Rows with PK feedback loop - sql

Question

Given the following (Table1):
Id Field1 Field2 ...
-- ------ -------
NULL 1 2
NULL 3 4
...
I'd like to insert the values of Field1 and Field2 into a different table (Table2). Table2 has an auto increment integer primary key. I want to retrieve the new PKs from Table2 and update the Id column above (Table1).
I realize this is not conventional - its not something I need to do regularly, simply one-off for some migration work. I made some attempts using INSERT INTO, OUTPUT, INSERTED.Id, but failed. The PKs that are "looped-back" into Table1 must tie to the values of Field1/Filed2 inserted.

Answer 1

You should just be able to do a insert, then a delete and re-insert.
create table t1
( id int, f1 int, f2 int);
create table t2
( id int primary key IDENTITY , f1 int, f2 int);
insert into t1 (id, f1, f2) values (null, 1, 2);
insert into t1 (id, f1, f2) values (null, 3, 4);
insert into t1 (id, f1, f2) values (null, 5, 6);
insert into t1 (id, f1, f2) values (null, 5, 6);
insert into t2 (f1, f2)
select f1, f2 from t1 where id is null;
delete t1
from t1 join t2 on (t1.f1 = t2.f1 and t1.f2 = t2.f2);
insert into t1
select id, f1, f2 from t2;
select * from t1;
See this example on SQLFiddle.

Answer 2

You will need some type of unique key to match your rows in each table. I've taken the liberty of adding a TempGuid column to each of your tables (which you can later drop):
-- Setup test data
declare #Table1 table (
Id int null
, Field1 int not null
, Field2 int not null
, TempGuid uniqueidentifier not null unique
)
insert into #Table1 (Field1, Field2, TempGuid) select 1, 2, newid()
insert into #Table1 (Field1, Field2, TempGuid) select 3, 4, newid()
declare #Table2 table (
Id int not null primary key identity(1, 1)
, Field1 int not null
, Field2 int not null
, TempGuid uniqueidentifier not null unique
)
-- Fill Table2
insert into #Table2 (Field1, Field2, TempGuid)
select Field1, Field2, TempGuid
from #Table1
-- Update Table1 with the identity values from Table2
update a
set a.Id = b.Id
from #Table1 a
join #Table2 b on a.TempGuid = b.TempGuid
-- Show results
select * from #Table1
Output would be workable if you already had a unique key on Table1 that you were inserting into Table2. You could also do a temporary unique key (perhaps GUID again) in a loop or cursor and process one row at a time, but that seems worse to me.
UPDATE
Here is the actual SQL to run on your tables:
-- Add TempGuid columns
alter table Table1 add TempGuid uniqueidentifier null
update Table1 set TempGuid = newid()
alter table Table2 add TempGuid uniqueidentifier not null
-- Fill Table2
insert into Table2 (Field1, Field2, TempGuid)
select Field1, Field2, TempGuid
from Table1
-- Update Table1 with the identity values from Table2
update a
set a.Id = b.Id
from Table1 a
join Table2 b on a.TempGuid = b.TempGuid
-- Remove TempGuid columns
alter table Table1 drop column TempGuid
alter table Table2 drop column TempGuid

Answer 3

Assuming you have full control over the schema definitions, add a foreign key to Table2 that references Table1's primary key.
Perform your data insert:
INSERT INTO Table2 (Field1, Field2, T1PK)
SELECT Field1, Field2, PK FROM Table1
Then backfill Table1:
UPDATE t1 SET Id = t2.PK
FROM Table1 t1 INNER JOIN Table2 t2 ON t2.T1PK = t1.PK
Then delete the extra column (T1PK) from Table2.
Edit:
Since there's no PK in Table1, just add one to Table1, use that, and then drop it at the end.
For example...
ALTER TABLE Table1 ADD COLUMN T1PK UNIQUEIDENTIFIER CONSTRAINT Table1_PK PRIMARY KEY DEFAULT NEWID();
ALTER TABLE Table2 ADD COLUMN T1PK UNIQUEIDENTIFIER NULL
INSERT INTO Table2 (Field1, Field2, T1PK)
SELECT Field1, Field2, T1PK FROM Table1
UPDATE t1 SET Id = t2.PK
FROM Table1 t1 INNER JOIN Table2 t2 ON t2.T1PK = t1.T1PK
ALTER TABLE Table1 DROP CONSTRAINT Table1_PK
ALTER TABLE Table1 DROP COLUMN T1PK
ALTER TABLE Table2 DROP COLUMN T1PK

Answer 4

This is not pretty, but should do as a one time effort.
create table tableA
(
id int,
field1 int,
field2 int
)
create table tableB
(
id int identity(1,1),
field1 int,
field2 int
)
insert into tableA select NULL, 1, 2
insert into tableA select NULL, 2, 3
declare #field1_value int;
declare #field2_value int;
declare #lastInsertedId int;
DECLARE tableA_cursor CURSOR FOR
select field1, field2 from tableA
OPEN tableA_cursor
FETCH NEXT FROM tableA_cursor INTO #field1_value, #field2_value
WHILE ##FETCH_STATUS = 0
BEGIN
insert into tableB select #field1_value, #field2_value
set #lastInsertedId = (SELECT SCOPE_IDENTITY())
update a
set id = #lastInsertedId
from tableA a
where field1 = #field1_value
and field2 = #field2_value
print #field1_value
FETCH NEXT FROM tableA_cursor
INTO #field1_value, #field2_value
END
CLOSE tableA_cursor
DEALLOCATE tableA_cursor
With not exists check:
declare #field1_value int;
declare #field2_value int;
declare #lastInsertedId int;
DECLARE tableA_cursor CURSOR FOR
select field1, field2 from tableA
OPEN tableA_cursor
FETCH NEXT FROM tableA_cursor INTO #field1_value, #field2_value
WHILE ##FETCH_STATUS = 0
BEGIN
IF NOT EXISTS
(
select * from tableB
where field1 = #field1_value
and field2 = #field2_value
)
BEGIN
insert into tableB
select #field1_value, #field2_value
set #lastInsertedId = (SELECT SCOPE_IDENTITY())
update a
set id = #lastInsertedId
from tableA a
where field1 = #field1_value
and field2 = #field2_value
END
FETCH NEXT FROM tableA_cursor
INTO #field1_value, #field2_value
END
CLOSE tableA_cursor
DEALLOCATE tableA_cursor