Explain The Rules For Updatable Join Views?

1.	Explain The Rules For Updatable Join Views?
Answer» General Rule Any INSERT, UPDATE, or DELETE OPERATION on a join view can modify only ONE underlying base table at a TIME. UPDATE Rule All updatable columns of a join view must map to columns of a key preserved table. If the view is defined with the WITH CHECK OPTION clause, then all join columns and all columns of repeated tables are non–updatable. DELETE Rule Rows from a join view can be deleted as long as there is exactly one key–preserved table in the join. If the view is defined with the WITH CHECK OPTION clause and the key preserved table is repeated, then the rows cannot be deleted from the view. INSERT Rule An INSERT statement must not, explicitly or implicitly, REFER to the columns of a non–key preserved table. If the join view is defined with the WITH CHECK OPTION clause, then INSERT statements are not PERMITTED.

Answer»

General Rule Any INSERT, UPDATE, or DELETE OPERATION on a join view can modify only ONE underlying base table at a TIME.
UPDATE Rule All updatable columns of a join view must map to columns of a key preserved table. If the view is defined with the WITH CHECK OPTION clause, then all join columns and all columns of repeated tables are non–updatable.
DELETE Rule Rows from a join view can be deleted as long as there is exactly one key–preserved table in the join. If the view is defined with the WITH CHECK OPTION clause and the key preserved table is repeated, then the rows cannot be deleted from the view.
INSERT Rule An INSERT statement must not, explicitly or implicitly, REFER to the columns of a non–key preserved table. If the join view is defined with the WITH CHECK OPTION clause, then INSERT statements are not PERMITTED.

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