Any user who needs to perform any form of update, delete, or insert operations, including the insert and update operations performed by a MERGE request, must be granted the SELECT privilege on all columns that are read by the delete, insert, merge, or update request from which that user needs to read values.
For the INSERT statement, SELECT privileges are required only if a table is to be reflexively grown by INSERT ... SELECT statements performed on itself.
If the column being updated, deleted, or inserted into has a UDT type, then you must also have the UDTUSAGE or UDTTYPE privilege on that UDT.
Be careful when granting the delete privilege through a view. A user who deletes a row through a view may accidently delete important data from columns not defined in the view.