Programs using a database API which conforms to the SQL standard receive an indication about the success or failure of the call. This return code - which is called SQLSTATE - consists of 5 bytes. They are divided into two parts: the first and second byte contains a class and the following three a subclass. Each class belongs to one of four categories: "S" denotes "Success" (class 00), "W" denotes "Warning" (class 01), "N" denotes "No data" (class 02) and "X" denotes "Exception" (all other classes).

The values of SQLSTATE are published and explained in Wikipedia.