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Category :
Database
Resources -> SQL and PLSQL
DB Version
:
Oracle 9i
OS Details :
Sun Solaris9
What
is a key-preserved table?
A table is key preserved if every
key of the table can also be a key of the result of the join. In other
words: when you join the key-preserved table, you won't get any row
duplication for the key-preserved table: a key-preserved table has its
keys preserved through a join.
For example,
if
you wrote an inline-update statement or a view that used multiple
table joins and produced a result set where the key of one of the
tables would uniquely identify the rows in the result set then the
table that the key is from is a key preserved table.
Sometimes, when updates are done against views, oracle runs in to a
situation where it cannot spot the key preserved attributes on the
table that you want updates to happen and raises the
ORA-1779 error: "cannot modify a column which maps to a non
key-preserved table".
When
such situation arise, there is a workaround for it and the workaround
involves the usage of a hint. The
bypass_ujvc
hint which stands
for bypass update join view check
can be used to overcome the ORA-1779 error.
Usage example:
UPDATE
/*+ BYPASS_UJVC */
(SELECT
.......)
SET
...... |
