UPDATE COLUMNS USING MAPPINGS

Question

I have to migrate data from one table to another where one of the columns is the same in both tables. e.g. ID COLUMN
Is there a way to migrate data such that I can update all rows in the ID column in table 2 with corresponding values from ID column in table 1 using one update statement?
i.e.
TABLE 1 || TABLE 2
ID || ID
2 || 5
5 || 9
8 || 4
34 || 98
67 || 762
89 || 99
I want to use 1 update statement if possible to update all rows in ID column table 2 with values in ID column in table 1
Thanks
Edited by: 331991 on Feb 4, 2010 11:04 PM

Answer 1

Hi,
You can do this by using cursor.
At First you have to save the id mapping relationship in a temp table, for example MAPPING_TABLE.
Then you can do this as follow:
Declare
    Cursor TO_UPDATE IS
    SELECT NEW.ID MEW_ID, NEW.COL1, NEW COL2,...., MAP.OLD_ID
    FROM NEW_TABLE NEW,
              MAPPING_TABLE MAP
    WHERE NEW.ID=MAP.NEW_ID
    ORDER BY OLD_ID;
Begin
    FOR REC IN  TO_UPDATE LOOP
         UPDATE OLD_TABLE
         SET ID=REC.NEW_ID,COL1=REC.COL1, COL2=REC.COL2, ....
         WHERE ID=REC.OLD_ID;
    END LOOP;
    COMMIT;
End; The better way, that you may let a column for control issue.
IF ATTRIBUTE1 is NULL for EACH ROW
Declare
    Cursor TO_UPDATE IS
    SELECT NEW.ID MEW_ID, NEW.COL1, NEW COL2,...., MAP.OLD_ID
    FROM NEW_TABLE NEW,
              MAPPING_TABLE MAP
    WHERE NEW.ID=MAP.NEW_ID
    ORDER BY OLD_ID;
Begin
    FOR REC IN  TO_UPDATE LOOP
         UPDATE OLD_TABLE
         SET ID=REC.NEW_ID,COL1=REC.COL1, COL2=REC.COL2, ...., ATTRIBUTE1 = REC.OLD_ID
         WHERE ID=REC.OLD_ID
         AND ATTRIBUTE1 IS NULL;
    END LOOP;
    COMMIT;
End; Best regards,
Zhxiang
Edited by: zhxiangxie on Feb 5, 2010 12:19 PM