(mysql.info.gz) mysql_field_count
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22.2.3.20 `mysql_field_count()'
...............................
`unsigned int mysql_field_count(MYSQL *mysql)'
If you are using a version of MySQL earlier than Version 3.22.24, you
should use `unsigned int mysql_num_fields(MYSQL *mysql)' instead.
Description
...........
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
`mysql_store_result()' should have produced a non-empty result. This
allows the client program to take proper action without knowing whether
the query was a `SELECT' (or `SELECT'-like) statement. The example
shown here illustrates how this may be done.
`NULL mysql_store_result()' NULL mysql_store_result.
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'.
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