MySQL - updating the average from one table into another table - mysql

Question

I'm a MYSQL/PHP newbie and I'm sure this is a simple question. I'm trying to calculate the average of several questions and respondents from one table and updating a Group table with that value.
For example Table answers consists of (name, group_id, TaskClarity1, TaskClarity2, TaskClarity3) in Table B i want (group_id, avg(TaskClarity1,TaskClarity2,TaskClarity3)).
This is what I've got...
$avg_task_clarity_1 = mysql_query("SELECT AVG(TaskClarity1) WHERE gruppid = '$group_id'");
$avg_task_clarity_2 = mysql_query("SELECT AVG(TaskClarity2) WHERE gruppid = '$group_id'");
$avg_task_clarity_3 = mysql_query("SELECT AVG(TaskClarity3) WHERE gruppid = '$group_id'");
$avg_task_clarity = ($avg_task_clarity_1+$avg_task_clarity_2+$avg_task_clarity_3)/3;
$print_task_clarity_1" UPDATE results SET results.TaskClarity = '$avg_task_clarity'";
if (mysql_query($print_task_clarity_1)) { echo $print_task_clarity_1; } else { echo "Error TaskClarity1: " . mysql_error();

Answer 1

First, mysql_query() returns a resource, and you then need to extract information from it. Your query doesn't mantion any table name (I'll call it MyTable).
Also, you can get all three averages with one query.
Here's how I would start:
$table = "MyTable";
$sql = "SELECT AVG(TaskClarity1) AS avgClarity1,
AVG(TaskClarity2) AS avgClarity2,
AVG(TaskClarity3) AS avgClarity1
FROM $table WHERE gruppid = '$group_id'";
$resource = mysql_query($sql); //execute the query
if (! $resource = mysql_query($sql) ){
echo "Error reading from table $table";
die;
}
if (! mysql_num_rows($resource ) ){
echo "No records found in $table";
}
else {
$row = mysql_fetch_assoc($resource); // fetch the first row
$avg_task_clarity_1 = $row['avgClarity1'];
$avg_task_clarity_2 = $row['avgClarity2'];
$avg_task_clarity_3 = $row['avgClarity3'];
$avg_task_clarity =
($avg_task_clarity_1+$avg_task_clarity_2+$avg_task_clarity_3)/3;
//...
// other stuff you want to do
}
Please comment if this is not helpful enough, and I will revise my answer.