25.2.3. C API Function Descriptions
In the descriptions here, a parameter or return value of
NULL means NULL in the
sense of the C programming language, not a MySQL
NULL value.
Functions that return a value generally return a pointer or an
integer. Unless specified otherwise, functions returning a
pointer return a non-NULL value to indicate
success or a NULL value to indicate an error,
and functions returning an integer return zero to indicate
success or non-zero to indicate an error. Note that
“non-zero” means just that. Unless the function
description says otherwise, do not test against a value other
than zero:
if (result) /* correct */
... error ...
if (result < 0) /* incorrect */
... error ...
if (result == -1) /* incorrect */
... error ...
When a function returns an error, the
Errors subsection of the
function description lists the possible types of errors. You can
find out which of these occurred by calling
mysql_errno(). A string representation of the
error may be obtained by calling
mysql_error().
