Question

I have two table. OLDTABLE and NEWTABLE.
I need to insert some data from oldtable to newtable and the get the ID from new table and update in the oldtable for that corresponding row. the newtable ID has seperate column in oldtable which is null by default.

One way is to get the ID from both table while inserting the data in new table and then later find the data in oldtable and update it. Which is simpler way.

Can anyone suggest some optimized way to do so?

Answer 1

Basically, there is no magic here – you need to insert the rows into newtable and keep track of the id’s – both the “old” ones from the oldtable as well as the new ones in new table.

So basically, you need something like this:

-- declare a helper table variable
DECLARE @TableOfID TABLE (OldID INT, NewID INT)  

-- insert rows into the "newtable" - OUTPUT the inserted ID (assuming it's INT IDENTITY)
-- and the "old ID" into the table variable
INSERT INTO dbo.newTable(OldID, Col1, Col2, ..., ColN)
OUTPUT Inserted.ID, Inserted.OldID INTO @TableOfID(NewID, OldID)
   SELECT 
       ID, Col1, Col2, .., ColN
   FROM 
       dbo.oldtable
   WHERE 
      ..... (some WHERE conditions here)

-- update the "oldtable"
UPDATE 
    dbo.oldtable
SET 
    NewID = t.NewID
FROM 
    @TableOfID t
WHERE
    dbo.oldtable.ID = t.OldID