Question

I have a table which doesnot have any unique key column and I want to perform bulk update using self join.

Update 
(
select t1.Col1 col1, t2.col1 col2
from table t1
inner join table t2 on <join condtn>
where <condtn>
)
Set col1 = col2

but as the table does not have unique key column, it gives error:

ORA-01779: cannot modify a column which maps to a non key-preserved
table.

Is there any solution other than adding unique constraint 🙂

Answer 1

You should be able to refactor the query to do a correlated update

UPDATE table t1
   SET col1 = (SELECT col1
                 FROM table t2
                WHERE t1.<<some column>> = t2.<<some column>>)
 WHERE EXISTS( SELECT 1
                 FROM table t2
                WHERE t1.<<some column>> = t2.<<some column>>)