如何使用PHP和MySQL从两个有条件链接的表中有效地SUM和SUBTRACT

Question

Is there a more efficient solution for the below query. I have tried to research the topic to the best of my ability but it's difficult to know what to actually search for...

$tenant_balance = 0;

$total_charge_amount_query = mysqli_query($con, "
    SELECT  tenant_charge_id, tenant_charge_total_amount
        FROM  accounts_tenant_charge
        WHERE  tenant_charge_tenancy_id='{$tenancy_details['tenancy_id']}'"
     ) or die(mysql_error());  

while($total_charge_amount_row = mysqli_fetch_array( $total_charge_amount_query )) {

    $tenant_balance = $tenant_balance +  $total_charge_amount_row['tenant_charge_total_amount'];

    $total_payment_amount_query = mysqli_query($con, "
        SELECT  tenant_charge_payment_amount
            FROM  accounts_tenant_charge_payment
            WHERE  tenant_charge_payment_tenant_charge_id =
                    '{$total_charge_amount_row['tenant_charge_id']}"
                 ) or die(mysql_error());

    while($total_payment_amount_row = mysqli_fetch_array( $total_payment_amount_query )) {

        $tenant_balance = $tenant_balance - $total_payment_amount_row['tenant_charge_payment_amount'];

    }
}

echo '£' . number_format($tenant_balance, 2, '.', ',');

I have added the database table structure and some data below.

Table #1

-- phpMyAdmin SQL Dump
-- version 4.0.10.7
-- http://www.phpmyadmin.net
--
-- Host: localhost
-- Generation Time: Jun 16, 2015 at 01:50 PM
-- Server version: 5.1.73-cll
-- PHP Version: 5.4.23

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";

--
-- Database: `propsyst_atlas`
--

-- --------------------------------------------------------

--
-- Table structure for table `accounts_tenant_charge`
--

CREATE TABLE IF NOT EXISTS `accounts_tenant_charge` (
  `tenant_charge_id` int(11) NOT NULL AUTO_INCREMENT,
  `tenant_charge_date` date DEFAULT NULL,
  `tenant_charge_payment_terms` tinyint(4) DEFAULT NULL,
  `tenant_charge_tenancy_id` int(11) DEFAULT NULL,
  `tenant_charge_notes` text COLLATE utf8_bin,
  `tenant_charge_total_amount` decimal(10,2) DEFAULT NULL,
  `tenant_charge_date_created` date DEFAULT NULL,
  `tenant_charge_date_updated` date DEFAULT NULL,
  `tenant_charge_created_by` int(11) DEFAULT NULL,
  `tenant_charge_updated_by` int(11) DEFAULT NULL,
  PRIMARY KEY (`tenant_charge_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=17 ;

--
-- Dumping data for table `accounts_tenant_charge`
--

INSERT INTO `accounts_tenant_charge` (`tenant_charge_id`, `tenant_charge_date`, `tenant_charge_payment_terms`, `tenant_charge_tenancy_id`, `tenant_charge_notes`, `tenant_charge_total_amount`, `tenant_charge_date_created`, `tenant_charge_date_updated`, `tenant_charge_created_by`, `tenant_charge_updated_by`) VALUES
(15, '2015-06-22', 1, 25, '', '180.00', '2015-06-14', '2015-06-14', 1, 1),
(14, '2015-06-15', 1, 25, '', '550.00', '2015-06-14', '2015-06-14', 1, 1),
(16, '2015-06-27', 1, 25, '', '10.00', '2015-06-14', '2015-06-14', 1, 1);

Table #2

-- phpMyAdmin SQL Dump
-- version 4.0.10.7
-- http://www.phpmyadmin.net
--
-- Host: localhost
-- Generation Time: Jun 16, 2015 at 01:51 PM
-- Server version: 5.1.73-cll
-- PHP Version: 5.4.23

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";

--
-- Database: `propsyst_atlas`
--

-- --------------------------------------------------------

--
-- Table structure for table `accounts_tenant_charge_payment`
--

CREATE TABLE IF NOT EXISTS `accounts_tenant_charge_payment` (
  `tenant_charge_payment_id` int(11) NOT NULL AUTO_INCREMENT,
  `tenant_charge_payment_date` date DEFAULT NULL,
  `tenant_charge_payment_amount` decimal(10,2) DEFAULT NULL,
  `tenant_charge_payment_method` tinyint(4) DEFAULT NULL,
  `tenant_charge_payment_tenant_charge_id` int(11) DEFAULT NULL,
  `tenant_charge_payment_notes` text COLLATE utf8_bin,
  `tenant_charge_payment_date_created` date DEFAULT NULL,
  `tenant_charge_payment_date_updated` date DEFAULT NULL,
  `tenant_charge_payment_created_by` int(11) DEFAULT NULL,
  `tenant_charge_payment_updated_by` int(11) DEFAULT NULL,
  PRIMARY KEY (`tenant_charge_payment_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=12 ;

--
-- Dumping data for table `accounts_tenant_charge_payment`
--

INSERT INTO `accounts_tenant_charge_payment` (`tenant_charge_payment_id`, `tenant_charge_payment_date`, `tenant_charge_payment_amount`, `tenant_charge_payment_method`, `tenant_charge_payment_tenant_charge_id`, `tenant_charge_payment_notes`, `tenant_charge_payment_date_created`, `tenant_charge_payment_date_updated`, `tenant_charge_payment_created_by`, `tenant_charge_payment_updated_by`) VALUES
(9, '2015-06-15', '550.00', 2, 14, '', '2015-06-14', '2015-06-14', 1, 1),
(10, '2015-06-22', '50.00', 2, 15, '', '2015-06-16', '2015-06-16', 1, 1);

Answer 1

I guess the point is to get rid of several queries and two PHP loops. With no need for loops, this query the calculate the total charge, payments and balance in one SQL query:

SELECT
    tenant_charge_tenancy_id,
    sum(tenant_charge_total_amount) as charge,
    IFNULL(sum(payments.payment), 0) as payment,
    sum(tenant_charge_total_amount) - IFNULL(sum(payments.payment), 0) as balance
FROM accounts_tenant_charge
LEFT OUTER JOIN (
    SELECT
        tenant_charge_payment_tenant_charge_id,
        sum(tenant_charge_payment_amount) as payment
    FROM accounts_tenant_charge_payment
    GROUP BY tenant_charge_payment_tenant_charge_id
) as payments ON tenant_charge_id = tenant_charge_payment_tenant_charge_id
WHERE tenant_charge_tenancy_id= 25
GROUP BY tenant_charge_tenancy_id

Instead of 25 you can put the $tenancy_details['tenancy_id'] in your PHP code. By removing the WHERE tenant_charge_tenancy_id= ... You can use this query to fetch all balances.

Answer 2

you are querying rows from account_tenant_charge with an id, like this

SELECT tenant_charge_id, tenant_charge_total_amount
  FROM accounts_tenant_charge
 WHERE tenant_charge_tenancy_id= ?

then for each row returned of that query, summing tenant_charge_total_amount in $tenant_balance , and querying (with each tenant_charge_id )

SELECT tenant_charge_payment_amount 
  FROM accounts_tenant_charge_payment 
 WHERE tenant_charge_payment_tenant_charge_id= ?

subtracting each tenant_charge_payment_amount from $tenant_balance .

First of all, you can do that with a single query that will be compiled once and executed on the server to provide a single result, preventing issuing a lot of queries that must be compiled and executed sequentially and transferring data back and forth between the web server and the dbms just to calculate a single result.

It'd be something like this

SELECT SUM(x.amount)
  FROM (SELECT tenant_charge_total_amount amount
          FROM accounts_tenant_charge
         WHERE tenant_charge_tenancy_id= ?
        UNION
        SELECT -tenant_charge_payment_amount amount
          FROM accounts_tenant_charge a
               JOIN accounts_tenant_charge_payment b
               ON tenant_charge_payment_tenant_charge_id = a.tenant_charge_id
         WHERE tenant_charge_tenancy_id= ?) x

Second, use bind variables and prepared statements ( see here ). If you build a dynamic query with each different id, you are forcing the db to compile the query each time, adding overhead to the execution time. Also dynamic queries are susceptible to sql injection attacks.

SQL is a declarative language, which means that you specify what you want to get and the dbms will execute it in the best way it finds. You should first rely on the db engine to optimize your queries. Looping through resultsets to issue repeating queries will most probably prevent the engine from optimizing and will add a lot of preventable overhead.

See DEMO here .

Answer 3

This query returns all tenant_charge_id and lists the total amount that needs to be paid as well as the total amount that has been paid already.

SELECT
    charge.tenant_charge_id,
    charge.tenant_charge_total_amount,
    SUM(payment.tenant_charge_payment_amount) total_payments
FROM  accounts_tenant_charge charge
LEFT JOIN accounts_tenant_charge_payment payment
    ON payment.tenant_charge_payment_tenant_charge_id = charge.tenant_charge_id
GROUP BY tenant_charge_id

You could add a WHERE clause to restrict the search for only a subset of tenants.

Answer 4

Try this:

SELECT tenant_charge_payment_tenant_charge_id, SUM(amount) balance
FROM (
   SELECT tenant_charge_payment_tenant_charge_id, tenant_charge_total_amount amount
   FROM accounts_tenant_charge 
   WHERE tenant_charge_tenancy_id='" . $tenancy_details['tenancy_id'] . "'   
   UNION
   SELECT tenant_charge_payment_tenant_charge_id, CONCAT('-',tenant_charge_payment_amount) amount
   FROM accounts_tenant_charge_payment 
   WHERE tenant_charge_payment_tenant_charge_id='" . $total_charge_amount_row['tenant_charge_id'] . "'
) temp
GROUP BY tenant_charge_payment_tenant_charge_id