Oracle 5.0, Reference Manual

Page: 2176 / 3232

C API Function Descriptions
2156
Return Values
An unsigned integer representing the number of columns in a result set.
Errors
None.
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_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: %s\n", 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 the statement was a
SELECT
.
20.6.6.23.
mysql_field_seek()
MYSQL_FIELD_OFFSET mysql_field_seek(MYSQL_RES *result, MYSQL_FIELD_OFFSET
offset)
Description
Sets the field cursor to the given offset. The next call to
mysql_fetch_field()
retrieves the field
definition of the column associated with that offset.
To seek to the beginning of a row, pass an
offset
value of zero.
Return Values
The previous value of the field cursor.
Errors
None.
20.6.6.24.
mysql_field_tell()