Restrictions for instead of

If a trigger references table names, column names, or view names that are not valid identifiers, you must set quoted_identifier on before the create trigger command, and enclose each such name in double quotation marks. The quoted_identifier option does not need to be on when the trigger fires; bracketed identifiers also work.

Using the set cursor rows command with client cursors, cursors declared through Open Client calls, or Embedded SQL™, may prevent positioned delete and update from firing an instead of trigger. A positioned update statement is a SQL update statement that contains the where current of <cursorname> clause to update only the row upon which the cursor, <cursorname>, is currently positioned.

Joins are not allowed in searched delete and update statements that would fire an instead of trigger.

positioned delete and update on cursors defined with joins does not fire an instead of trigger.

A positioned delete (or positioned update) is a SQL delete (or update) statement containing a where current of <cursorname> clause to delete (or update) only the row upon which the cursor, <cursorname>, is currently positioned.

For positioned delete and update statements that fire an instead of trigger, the instead of trigger must exist when the cursor is declared.