C.2. Types of Error Values

When an error occurs in MySQL, the server returns two types of error values:

A MySQL-specific error code. This value is numeric. It is not portable to other database systems.
An SQLSTATE value. The value is a five-character string (for example, '42S02'). The values are taken from ANSI SQL and ODBC and are more standardized.

A message string that provides a textual description of the error is also available.

When an error occurs, the MySQL error code, SQLSTATE value, and message string are available using C API functions:

For prepared statements, the corresponding error functions are mysql_stmt_errno(), mysql_stmt_sqlstate(), and mysql_stmt_error(). All error functions are described in Section 22.8, "MySQL C API".

The number of errors, warnings, and notes for the previous statement can be obtained by calling mysql_warning_count(). See Section 22.8.7.73, "mysql_warning_count()".

The first two characters of an SQLSTATE value indicate the error class:

Class = '00' indicates success.
Class = '01' indicates a warning.
Class = '02' indicates "not found." This is relevant within the context of cursors and is used to control what happens when a cursor reaches the end of a data set. This condition also occurs for SELECT ... INTO var_list statements that retrieve no rows.
Class > '02' indicates an exception.