docs: add "Logging All SQL Queries"

Author: kenjis

user_guide_src/source/database/events.rst

@@ -15,6 +15,8 @@ uses this to collect the queries to display in the Toolbar.
 The Events
 **********
 
+.. _database-events-dbquery:
+
 DBQuery
 =======
 
@@ -26,6 +28,6 @@ You could use this to display all queries in STDOUT, or logging to a file, or
 even creating tools to do automatic query analysis to help you spot potentially
 missing indexes, slow queries, etc.
 
-An example usage might be:
+An example to log all queries:
 
 .. literalinclude:: events/001.php

user_guide_src/source/testing/debugging.rst

@@ -23,6 +23,12 @@ It would be a good idea to check them if things aren't working the way you expec
 You can adjust the error threshold to see more or fewer messages. See
 :ref:`Logging <logging-configuration>` for details.
 
+Logging All SQL Queries
+=======================
+
+All SQL queries issued by CodeIgniter can be logged.
+See :ref:`Database Events <database-events-dbquery>` for details.
+
 ********************
 Replacing var_dump()
 ********************