Getting total in while statement with UNION query - php

Question

I am trying to calculate how much a user has earned so it reflects on the users home page so they know how much their referrals have earned.
This is the code I have.
$get_ref_stats = $db->query("SELECT * FROM `members` WHERE `referral` = '".$user_info['username']."'");
$total_cash = 0;
while($ref_stats = $get_ref_stats->fetch_assoc()){
$get_ref_cash = $db->query("SELECT * FROM `completed` WHERE `user` = '".$ref_stats['username']."' UNION SELECT * FROM `completed_repeat` WHERE `user` = '".$ref_stats['username']."'");
$countr_cash = $get_ref_cash->fetch_assoc();
$total_cash += $countr_cash['cash'];
$countr_c_rate = $setting_info['ref_rate'] * 0.01;
$total_cash = $total_cash * $countr_c_rate;
}
It worked fine when I just had
$get_ref_cash = $db->query("SELECT * FROM `completed` WHERE `user` = '".$ref_stats['username']."'");
but as soon as I added in the UNION it no longer calculated correctly.
For example, there is 1 entry in completed and 1 entry in completed_repeat both of these entries have a cash entry of 0.75. The variable for $countr_c_rate is 0.10 so $total_cash should equal 0.15 but instead it displays as 0.075 with and without the UNION it acts as if it is not counting from the other table as well.
I hope this makes sense as I wasn't sure how to explain the issue, but I am very unsure what I have done wrong here.

Answer 1

In your second query instead of UNION you should use UNION ALL since UNION eliminates duplicates in the resultset. That is why you get 0.075 instead of 0.15.
Now, instead of hitting your database multiple times from client code you better calculate your cash total in one query.
It might be inaccurate without seeing your table structures and sample data but this query might look like this
SELECT SUM(cash) cash_total
FROM
(
SELECT c.cash
FROM completed c JOIN members m
ON c.user = m.username
WHERE m.referral = ?
UNION ALL
SELECT r.cash
FROM completed_repeat r JOIN members m
ON r.user = m.username
WHERE m.referral = ?
) q
Without prepared statements your php code then might look like
$sql = "SELECT SUM(cash) cash_total
FROM
(
SELECT c.cash
FROM completed c JOIN members m
ON c.user = m.username
WHERE m.referral = '$user_info['username']'
UNION ALL
SELECT r.cash
FROM completed_repeat r JOIN members m
ON r.user = m.username
WHERE m.referral = '$user_info['username']'
) q";
$result = $db->query($sql);
if(!$result) {
die($db->error()); // TODO: better error handling
}
if ($row = $result->fetch_assoc()) {
$total_cash = $row['cash_total'] * $setting_info['ref_rate'];
}
On a side note: make use of prepared statements in mysqli instead of building queries with concatenation. It's vulnerable for sql-injections.

Answer 2

With $countr_cash = $get_ref_cash->fetch_assoc(); you only fetch the first row of your result. However, if you use UNION, you get in your case two rows.
Therefore, you need to iterate over all rows in order to get all values.

Answer 3

Ok, So there is only one row in members table. You are iterating only once on the members table. Then you are trying to get rows using UNION clause which will result in two rows and not one. Then you are just getting the cash column of the first row and adding it to the $total_cash variable.
What you need to do is iterate over the results obtained by executing the UNION query and add the $total_cash variable. That would give you the required result.
$get_ref_stats = $db->query("SELECT * FROM `members` WHERE `referral` = '".$user_info['username']."'");
$total_cash = 0;
while($ref_stats = $get_ref_stats->fetch_assoc()){
$get_ref_cash = $db->query("SELECT * FROM `completed` WHERE `user` = '".$ref_stats['username']."' UNION SELECT * FROM `completed_repeat` WHERE `user` = '".$ref_stats['username']."'");
while($countr_cash = $get_ref_cash->fetch_assoc()){
$total_cash += $countr_cash['cash'];
}
$countr_c_rate = $setting_info['ref_rate'] * 0.01;
$total_cash = $total_cash * $countr_c_rate;
}