Sams Teach Yourself MySQL in 21 Days, Second Edition

mysql_error([link_identifier])

Description: Returns the error message text from the previous MySQL operation, or the empty string if no error occurred.

Example:

if ($result = mysql_query ("select * from bad_table")) {
    # query worked okay, keep going
} else {
    echo "A database error occurred!<BR>\n";
    echo mysql_error() ." (error no. ". mysql_errno() .")<BR>\n";
    exit;
}

See also: mysql_errno()