multiple sum in my sql - mysql

Question

Trying to get result in single query however unable to get correct sum of order stock, it display sum twice if waste item exits.
Please see below query
SELECT DISTINCT cd.id,i.*,c.category_name, SUM(CASE WHEN s.stock_type = 'f' THEN s.stock END) AS instock, SUM(CASE WHEN s.stock_type = 'w' THEN s.stock END) AS weststock, SUM(cd.qty) AS orderstock, IF(SUM(CASE WHEN s.stock_type = 'f' THEN s.stock END) IS NULL,0, SUM(CASE WHEN s.stock_type = 'f' THEN s.stock END)) - IF(SUM(CASE WHEN s.stock_type = 'w' THEN s.stock END) IS NULL,0, SUM(CASE WHEN s.stock_type = 'w' THEN s.stock END)) - IF(SUM(cd.qty) IS NULL,0, SUM(cd.qty)) AS total
FROM item AS i
JOIN categories AS c ON i.category_id = c.id
LEFT JOIN stock AS s ON i.id=s.item_id
LEFT JOIN manage_godown AS mg ON mg.id = s.godown_id
LEFT JOIN cart_detail AS cd ON i.id=cd.item_id AND cd.cart_id IN (
SELECT ca.id
FROM cart AS ca
WHERE ca.status ='o')
WHERE mg.id=8
GROUP BY i.id
ORDER BY i.id DESC
Table Structure
----------------------
--
-- Table structure for table `admin`
--
CREATE TABLE IF NOT EXISTS `admin` (
`id` double NOT NULL AUTO_INCREMENT,
`email` varchar(255) NOT NULL,
`name` varchar(255) NOT NULL,
`mobile_no` varchar(50) NOT NULL,
`password` varchar(255) NOT NULL,
`status` enum('a','d') NOT NULL COMMENT 'a= active,d=deactive',
`type` enum('a','m') NOT NULL DEFAULT 'm',
`last_login` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`change_password_key` text NOT NULL,
`isAsigned` enum('y','n') NOT NULL DEFAULT 'n',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;
-- --------------------------------------------------------
--
-- Table structure for table `area`
--
CREATE TABLE IF NOT EXISTS `area` (
`id` double NOT NULL AUTO_INCREMENT,
`area_name` varchar(255) NOT NULL,
`area_status` enum('a','d') NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ;
-- --------------------------------------------------------
--
-- Table structure for table `cart`
--
CREATE TABLE IF NOT EXISTS `cart` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` double NOT NULL,
`date` datetime NOT NULL,
`status` enum('c','o') NOT NULL DEFAULT 'c',
`ship_status` enum('y','n') NOT NULL DEFAULT 'n',
`shiping_address` text NOT NULL,
`order_date` datetime NOT NULL,
`area_id` int(11) NOT NULL,
`user_name` varchar(255) NOT NULL,
`email` varchar(255) NOT NULL,
`contact_number` varchar(255) NOT NULL,
`address` text NOT NULL,
`shipping_name` varchar(255) NOT NULL,
`order_delivery_status` enum('p','d','c') NOT NULL COMMENT 'p=pending,d=deliverd,c=cancle',
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=10 ;
-- --------------------------------------------------------
--
-- Table structure for table `cart_detail`
--
CREATE TABLE IF NOT EXISTS `cart_detail` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`cart_id` int(11) NOT NULL,
`item_id` int(11) NOT NULL,
`qty` double NOT NULL,
`amount` double NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=13 ;
-- --------------------------------------------------------
--
-- Table structure for table `categories`
--
CREATE TABLE IF NOT EXISTS `categories` (
`id` double NOT NULL AUTO_INCREMENT,
`category_name` varchar(255) NOT NULL,
`isDefault` enum('y','n') NOT NULL DEFAULT 'n',
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
-- --------------------------------------------------------
--
-- Table structure for table `item`
--
CREATE TABLE IF NOT EXISTS `item` (
`id` double NOT NULL AUTO_INCREMENT,
`category_id` double NOT NULL,
`item_name` varchar(255) NOT NULL,
`item_image` text NOT NULL,
`price` double NOT NULL,
`isPopular` enum('Y','N') NOT NULL,
`item_status` enum('a','d') NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=34 ;
-- --------------------------------------------------------
--
-- Table structure for table `manage_godown`
--
CREATE TABLE IF NOT EXISTS `manage_godown` (
`id` double NOT NULL AUTO_INCREMENT,
`godown_name` varchar(150) NOT NULL,
`address` text NOT NULL,
`contact_number` varchar(50) NOT NULL,
`contact_person` varchar(255) NOT NULL,
`area_id` text NOT NULL,
`user_id` varchar(100) NOT NULL,
`godown_status` enum('a','d') NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;
--
-- Dumping data for table `area`
--
INSERT INTO `area` (`id`, `area_name`, `area_status`) VALUES
(1, 'C.G. Road', 'a'),
(2, 'S.G. Highway', 'a'),
(3, 'Bopal', 'a'),
(4, 'New Wadaj', 'a'),
(5, 'Ranip', 'a'),
(6, 'Bapunagar', 'a'),
(7, 'Gurukul RD', 'a'),
(8, 'Ghatlodia', 'a'),
(9, 'Nehru Nagar', 'a'),
(10, 'Old Wadaj', 'a'),
(11, 'Paldi', 'a'),
(12, 'NaranPura', 'a'),
(13, 'Anand Nagar', 'd'),
(14, 'Shahpur', 'a');
--
-- Dumping data for table `cart`
--
INSERT INTO `cart` (`id`, `user_id`, `date`, `status`, `ship_status`, `shiping_address`, `order_date`, `area_id`, `user_name`, `email`, `contact_number`, `address`, `shipping_name`, `order_delivery_status`) VALUES
(1, 1, '2015-03-09 20:30:36', 'o', 'n', 'roam', '2015-03-09 21:14:45', 7, 'account1', 'account1#superrito.com', '123456', 'roam', 'account1', 'p'),
(2, 1425936687, '2015-03-09 21:31:27', 'c', 'n', '', '0000-00-00 00:00:00', 0, '', '', '', '', '', 'p'),
(3, 1426012764, '2015-03-10 18:39:24', 'c', 'n', '', '0000-00-00 00:00:00', 0, '', '', '', '', '', 'p');
--
-- Dumping data for table `cart_detail`
--
INSERT INTO `cart_detail` (`id`, `cart_id`, `item_id`, `qty`, `amount`) VALUES
(1, 1, 1, 3, 80),
(2, 2, 1, 0.25, 80),
(3, 3, 1, 0.5, 80),
(4, 3, 2, 0.25, 45);
--
-- Dumping data for table `categories`
--
INSERT INTO `categories` (`id`, `category_name`, `isDefault`) VALUES
(1, 'vegitables', 'y'),
(2, 'fruits', 'y');
--
-- Dumping data for table `item`
--
INSERT INTO `item` (`id`, `category_id`, `item_name`, `item_image`, `price`, `isPopular`, `item_status`) VALUES
(1, 1, 'Tomato', '210fc803a958749e7b2a55c32c744f13.png', 80, 'Y', 'a'),
(2, 1, 'Potato', 'c244be2eab10bc46465d5b36448ba68b.jpg', 45, 'N', 'a'),
(3, 2, 'Cabbige', '05423c579cc99709923273c5222c4661.jpg', 120, 'Y', 'a');
--
-- Dumping data for table `manage_godown`
--
INSERT INTO `manage_godown` (`id`, `godown_name`, `address`, `contact_number`, `contact_person`, `area_id`, `user_id`, `godown_status`) VALUES
(8, 'Gurukul', 'Gurukul RD', '12457894', 'Salim', '7', '16', 'a'),
(9, 'Godown2', 'Godown2', '123456798', 'Samln', '12', '17', 'a');
--
-- Dumping data for table `user`
--
INSERT INTO `user` (`id`, `email`, `user_name`, `address`, `shiping_address`, `mobile_no`, `password`, `isVeryfied`, `created_date`, `email_verification`, `change_password_key`, `area_id`, `pincode`, `user_status`) VALUES
(1, 'account1#superrito.com', 'account1', 'roam', 'roam', '123456', '4b111bc4e9e96cd1d18d0359fdb94629', 'n', '2015-03-09 08:53:00', '', '', 0, 0, 'a'),
(2, 'tripathi_hhh#yahoo.com', 'hitesh tripathi', '', '', '9033913397', 'e10adc3949ba59abbe56e057f20f883e', 'n', '2015-03-10 06:31:23', '17a962a2eee74445747a3e194da6c556', 'be45b6a9362c65217ec88821b648a67f', 0, 0, 'a');
I placed order of Tomato 3KG Only however i added wasted item 3 times so sum of above query gives result 12KG in orderstock

Answer 1

Using COALESCE instead of IF ... IS NULL makes it a lot more readable... I'm waiting on your answer to #EdwinKrause's question to help with the rest.
SELECT DISTINCT cd.id,i.*,c.category_name,
SUM(CASE WHEN s.stock_type = 'f' THEN s.stock END) AS instock,
SUM(CASE WHEN s.stock_type = 'w' THEN s.stock END) AS weststock,
SUM(cd.qty) AS orderstock,
COALESCE( SUM(CASE WHEN s.stock_type = 'f' THEN s.stock END), 0) -
COALESCE(SUM(CASE WHEN s.stock_type = 'w' THEN s.stock END), 0) -
COALESCE(SUM(cd.qty), 0) AS total
FROM item AS i
JOIN categories AS c ON i.category_id = c.id
LEFT JOIN stock AS s ON i.id=s.item_id
LEFT JOIN manage_godown AS mg ON mg.id = s.godown_id
LEFT JOIN cart_detail AS cd ON i.id=cd.item_id AND cd.cart_id IN (
SELECT ca.id
FROM cart AS ca
WHERE ca.status ='o')
WHERE mg.id=2
GROUP BY i.id
ORDER BY i.id DESC