UPDATE COLS OF ONE TABLE FROM VALUES OF CERTAIN COLU OF ANOTHER TABLE

Question

I have two tables table1               table1     
(col1,                (col1,
          col2,                col2,
          col3,                col3,
          col4,                col4,
          timeperiod)                timeperiod)
both have same column names. table1 has data for certain timeperiod. table2 also has the data for the same timeperiod. table2 has the correct data for col1, col2. I want to update the columns (col1, col2) in table1 with data from columns (col1, col2) in table2
and leave the col3, col4 in table1 untouched (no change). Each time I might have to update different columns. some tables have more than 20 columns. This is like, I need to update whatever field I want.
How do I do this with a script or block declaring variables. How do I control the update for certain columns. This is not a one time thing which I will be doing. I have to do this for several tables whenever the data is not right.
Thank you,
sv

Answer 1

Hi ,
you can use MERGE for this kind of situations....here i have given some samples...refer this...
MERGE INTO bonuses D
USING (SELECT employee_id, salary, department_id FROM employees
WHERE department_id = 80) S
ON (D.employee_id = S.employee_id)
WHEN MATCHED THEN UPDATE SET D.bonus = D.bonus + S.salary*.01
WHEN NOT MATCHED THEN INSERT (D.employee_id, D.bonus)
VALUES (S.employee_id, S.salary*0.1);
By this way u can update any no. of columns...I hope this will help you...
Thanks
Raj