27.3.6.6 Warning Object

Warning represents a warning raised by statement execution, and has the following properties:

code: MySQL error code (integer).
level: Warning level. Can be any one of 1 (NOTE), 2 (WARNING), or 3 (ERROR).
message: Text of the warning message; a string.

You can also employ the JavaScript Error object, such as obtained from a try-catch block. See Error Handling, for more information.