mysql_num_fields problem

Mr_Mako

Hi...

I'm attempting to get a result from a field in a database. The query I am running is exampled below:

$kia_pilot = "SELECT cas_pilot FROM mission WHERE cas_pilot = '4' AND mission_no = '$mission' AND plane_name = '$pb'";
$kia_pilot_result = @mysql_query($kia_pilot, $connect) or die(mysql_error());

$num_p_kia = mysql_num_fields($kia_pilot_result);

I only want mysql_num_fields to return a result above 0 if the query listed is "correct".

What I'm getting for $num_p_kia is "1". I don't understand why, since the database I'm looking into has an integer DIFFERENT than '4' in the "cas_pilot" field.

Do I have this query set up wrong? Or am I using the wrong function to attempt to get my result?

laserlight

um, mysql_num_fields() gets number of fields from a result.
I suspect that when no rows are returned, there still is some default that can be counted as a field.

I suggest you use [man]mysql_num_rows/man instead for what you intend to do.

Mr_Mako

Ok... well, num_rows won't work because I'm trying to get the results of a single field. The reason being is that I am querying 10 different fields from a single record individually, and the num_rows function will just yeild me the record (or row) result, which isn't what I'm looking for.

The example above is just one of the query's of the 10 different one's I'm trying to get (they all just reference a different field).

Am I going to have to capture the results of the individual fields in a 'while' statement? That'd be a lot of extra work, but if it's the only way I can accomplish this...

I probably should add that I'm not necessarily interested in the contents of the fields... just whether it contains '4' or not. Basically a binary question - "If field contains '4' then 1, else 0."

laserlight

"num_rows won't work because I'm trying to get the results of a single field"
And mysql_num_fields() will work?
Here's a test:
SELECT cas_pilot, mission FROM mission WHERE cas_pilot = '4' AND mission_no = '' AND plane_name = 'no_plane_haha'
Try the above query instead, and tell me your results.
mysql_num_fields() should return 2.
mysql_num_rows() should return 0, unless you have a row where cas_pilot='4', an empty mission_no and a funny plane named 'no_plane_haha'

Why?
mysql_num_fields(), as mentioned, returns the number of fields in a result set.
This is the number of fields that you wish to have selected.
Normally one would use this for say, a "SELECT * FROM" type of query, to dynamically get the number of fields.
For a "SELECT column1, column2, columnN FROM" type of query, it will return N, assuming that the query is correct.
This is independent of the number of rows returned in the query.

mysql_num_rows() returns the number of rows in the result set (i.e. returned from running the query).
The query that you are running will return [0,n] rows, where n is the number of rows in the table.
Within each row retrieved, however, is only 1 field, from the cas_pilot column.

But you know that the field must contain the value of 4, since that is one of the requirements in WHERE.
So, if there are m rows that have cas_pilot='4', then the result set will return [0,m] rows.

As such, if there is 1 row that fulfills all your requirements, you will get the answer of 1.
If there are none, you will get 0.

EDIT: typo

Mr_Mako

Thanks for the detailed reply.

Apparently, I've misunderstood the usage of mysql_num_fields. As a result of your explanation of both of those functions, I've realized that to get the results I'm looking for, neither num_fields or num_rows will work.

I'm going to have to make a query call to each of the ten fields, get the contents, and then run an 'if/else' statement on them to get what I'm looking for I guess. I had thought there was an easier way to do that, but either I'm not familiar enough with some of the more complex php functions or there isn't any other way to do it.