problem in getting count - sql

Question

Here is my table complete schema , i want to get the each category sale count ,
How to get that each category sale count ,
CREATE TABLE IF NOT EXISTS `tblbasket` (
`BID` int(20) NOT NULL
AUTO_INCREMENT,
`BasketSessionID` varchar(100) NOT NULL DEFAULT '0',
`ProductCode` varchar(50) NOT NULL,
`Quantity` int(20) NOT NULL,
`AfterDiscount` double NOT NULL DEFAULT '0',
`ProductCost` double NOT NULL,
`SaleMode` varchar(10) NOT NULL DEFAULT 'p' COMMENT 'p Price f Free',
`BillType` varchar(5) NOT NULL DEFAULT 's' COMMENT 's sale r Returns',
`EntryUser` int(20) NOT NULL,
`EntryTimestamp` int(50) NOT NULL,
`EntryDate` datetime NOT NULL,
`UpdatedUser` int(20) NOT NULL,
`UpdatedDate` datetime NOT NULL,
`Status` int(3) NOT NULL DEFAULT '1',
PRIMARY KEY (`BID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;
CREATE TABLE IF NOT EXISTS `tblcategory` (
`CatID` int(11) NOT NULL AUTO_INCREMENT,
`CatName` varchar(20) NOT NULL,
`Discount` int(11) NOT NULL,
`EntryUser` int(10) NOT NULL,
`EntryDate` datetime NOT NULL,
`UpdateUser` int(20) NOT NULL,
`UpdatedDate` datetime NOT NULL,
`Status` int(3) NOT NULL DEFAULT '1',
PRIMARY KEY (`CatID`),
KEY `CatName` (`CatName`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;
CREATE TABLE IF NOT EXISTS `tblsale` ( `SaleID` int(20) NOT NULL AUTO_INCREMENT,
`BillNo` varchar(30) NOT NULL DEFAULT '0',
`BasketSessionID` varchar(200) NOT NULL,
`AfterDiscount` double NOT NULL,
`ProductCost` double NOT NULL, `VAT` int(20) NOT NULL DEFAULT '0',
`BillType` varchar(5) NOT NULL DEFAULT 's' COMMENT 'same like tblbasket table',
`EntryUser` int(20) NOT NULL,
`EntryDate` datetime NOT NULL,
`UpdatedUser` int(20) NOT NULL,
`UpdateDate` datetime NOT NULL,
`OfficeNotesTS` text NOT NULL,
`Status` int(5) NOT NULL DEFAULT '1',
PRIMARY KEY (`SaleID`),
UNIQUE KEY `BillNo` (`BillNo`),
UNIQUE KEY `BasketSessionID` (`BasketSessionID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;
CREATE TABLE IF NOT EXISTS `tblstock` (
`StockID` int(20) NOT NULL AUTO_INCREMENT,
`ProductCode` varchar(50) NOT NULL,
`ManufacturerID` int(20) NOT NULL,
`CategoryID` int(20) NOT NULL,
`ProductTitle` varchar(150) NOT NULL,
`Timestamp` int(50) NOT NULL,
`EntryUser` int(20) NOT NULL,
`EntryDate` datetime NOT NULL,
`UpdateUser` int(20) NOT NULL,
`UpdatedDate` datetime NOT NULL,
`Status` int(3) NOT NULL DEFAULT '1',
PRIMARY KEY (`StockID`),
KEY `ManufacturerID` (`ManufacturerID`),
KEY `CategoryID` (`CategoryID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2175 ;
CREATE TABLE IF NOT EXISTS `tblstockhistory` (
`STID` int(20) NOT NULL AUTO_INCREMENT,
`StockID` int(20) NOT NULL,
`SupplierID` int(20) NOT NULL,
`InvoiceNO` varchar(20) NOT NULL,
`InvoiceDate` datetime NOT NULL,
`InvoiceAmount` float NOT NULL DEFAULT '0',
`Quantity` int(20) NOT NULL,
`Cost` float NOT NULL,
`MRP` float NOT NULL,
`Discount` int(20) NOT NULL DEFAULT '0',
`VAT` float NOT NULL,
`EntryUser` int(10) NOT NULL,
`EntryDate` datetime NOT NULL,
`UpdateUser` int(20) NOT NULL,
`UpdatedDate` datetime NOT NULL,
`Status` int(10) NOT NULL DEFAULT '1',
PRIMARY KEY (`STID`),
KEY `StockID` (`StockID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2190 ;
ALTER TABLE `tblstock`
ADD CONSTRAINT `tblStock_ibfk_1`
FOREIGN KEY (`ManufacturerID`)
REFERENCES `tblmanufacturer` (`ManufacturerID`);
ALTER TABLE `tblstockhistory`
ADD CONSTRAINT `tblStockHistory_ibfk_1`
FOREIGN KEY (`StockID`)
REFERENCES `tblstock` (`StockID`);

Answer 1

try something like that (its hard to understand without foreign key, and little explain ):
SELECT st.CategoryID,SUM(b.ProductCost*b.Quantity) FROM tblsale s
LEFT JOIN tblbasket b ON b.BasketSessionID = s.BasketSessionID
LEFT JOIN tblstock st ON st.ProductCode = b.ProductCode GROUP BY st.CategoryID