MySQL :: MySQL 8.4 C API Developer Guide :: 5.4.52 mysql_num_fields() (original) (raw)

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5.4.52 mysql_num_fields()

unsigned int
mysql_num_fields(MYSQL_RES *result)

To pass a MYSQL* argument instead, useunsigned int mysql_field_count(MYSQL *mysql).

Return Values

An unsigned integer representing the number of columns in a result set.

Example

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_errno(&mysql))
        {
           fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
        }
        else if (mysql_field_count(&mysql) == 0)
        {
            // query does not return data
            // (it was not a SELECT)
            num_rows = mysql_affected_rows(&mysql);
        }
    }
}

An alternative (if you know that your query should have returned a result set) is to replace themysql_errno(&mysql) call with a check whethermysql_field_count(&mysql) returns 0. This happens only if something went wrong.