MySQL 5.7 C API Developer Guide
my_ulonglong mysql_stmt_insert_id(MYSQL_STMT *stmt)
Returns the value generated for an
AUTO_INCREMENT column by the prepared
INSERT or
UPDATE statement. Use this
function after you have executed a prepared
INSERT statement on a table
which contains an AUTO_INCREMENT field.
See Section 5.4.38, “mysql_insert_id()”, for more information.
Value for AUTO_INCREMENT column which was
automatically generated or explicitly set during execution of
prepared statement, or value generated by
LAST_INSERT_ID(
function. Return value is undefined if statement does not set
expr)AUTO_INCREMENT value.