Fix #27 - Created rule G-7720: Never use multiple UPDATE OF in trigger event clause.

Author: kibeha

docs/4-language-usage/7-stored-objects/2-packages/g-7240.md

@@ -5,7 +5,7 @@
 
 ## Reason
 
-The purpose of the initialization block of a package body is to set initial values of the global variables of the package (initialize the package state). Although `RETURN` is syntactically allowed in this block, it makes no sense. If it is the last keyword of the block, it is superfluous. If it is not the last keyword, then all code after the `RETURN` is unreachable and thus dead code.
+The purpose of the initialization block of a package body is to set initial values of the global variables of the package (initialize the package state). Although `return` is syntactically allowed in this block, it makes no sense. If it is the last keyword of the block, it is superfluous. If it is not the last keyword, then all code after the `return` is unreachable and thus dead code.
 
 ## Example (bad)
 

docs/4-language-usage/7-stored-objects/7-triggers/g-7720.md

@@ -0,0 +1,43 @@
+# G-7720: Never use multiple UPDATE OF in trigger event clause.
+
+!!! bug "Blocker"
+    Maintainability, Reliability, Testability
+
+## Reason
+
+A DML trigger can have multiple triggering events separated by `or` like `before insert or delete or update of some_column`. If you have multiple `update of` separated by `or`, only one of them (the last one) is actually used and you get no error message, so you have a bug waiting to happen. Instead you always should use a single `update of` with all columns comma-separated, or an `update` without `of` if you wish all columns.
+
+## Example (bad)
+
+``` sql
+create or replace trigger dept_br_u
+before update of department_id or update of department_name
+on departments for each row
+begin
+   -- will only fire on updates of department_name
+   insert into departments_log (department_id
+                               ,department_name
+                               ,modification_date) 
+                        values (:old.department_id
+                               ,:old.department_name
+                               ,sysdate);
+end;
+/
+```
+
+## Example (good)
+
+``` sql
+create or replace trigger dept_br_u
+before update of department_id, department_name
+on departments for each row
+begin
+   insert into departments_log (department_id
+                               ,department_name
+                               ,modification_date) 
+                        values (:old.department_id
+                               ,:old.department_name
+                               ,sysdate);
+end;
+/
+```