mysql_field_count()
unsigned int mysql_field_count(MYSQL *mysql)
If you are using a version of MySQL earlier than 3.22.24, you
should use unsigned int mysql_num_fields(MYSQL *mysql) instead.
Returns the number of columns for the most recent query on the connection.
The normal use of this function is when mysql_store_result()
returned NULL (and thus you have no result set pointer).
In this case, you can call mysql_field_count() to
determine whether or not mysql_store_result() should have produced a
non-empty result. This allows the client program to take proper action
without knowing whether or not the query was a SELECT (or
SELECT-like) statement. The example shown below illustrates how this
may be done.
An unsigned integer representing the number of fields in a result set.
None.
MYSQL_RES *result;
unsigned int num_fields;
unsigned int num_rows;
if (mysql_query(&mysql,query_string))
{
// error
}
else // query succeeded, process any data returned by it
{
result = mysql_store_result(&mysql);
if (result) // there are rows
{
num_fields = mysql_num_fields(result);
// retrieve rows, then call mysql_free_result(result)
}
else // mysql_store_result() returned nothing; should it have?
{
if(mysql_field_count(&mysql) == 0)
{
// query does not return data
// (it was not a SELECT)
num_rows = mysql_affected_rows(&mysql);
}
else // mysql_store_result() should have returned data
{
fprintf(stderr, "Error:@: %sn", mysql_error(&mysql));
}
}
}
An alternative is to replace the mysql_field_count(&mysql) call with
mysql_errno(&mysql). In this case, you are checking directly for an
error from mysql_store_result() rather than inferring from the value
of mysql_field_count() whether or not the statement was a
SELECT.