by using SQL COMMAND

Q1) Create a complete project using SQL/PLSQL programing language to achieve the following requirement to develop point of sale system which allow the Employee to add customer invoice which contain his/her invoice information such as customer name, employee name who create this invoice which contain invoice date and total price with its related purchased items which contain quantity and price for each item in customer invoice. Follow these requirements 1) Design database schema and create database user "pointOfSal" that contain database schema tables with its related relationships and database constraints 2) Grant the pointOfSal user all privileges that needed by database designer and developer to create database schema 3) The system must contain tables such as category(catNo , catogeryName) ,Items(itemNo,ItemName,Price,total_quantity, catNo), Items_stor_entry(entry_no number primary key,itemNo,entry_date ,quantity), Employee (employeeNo,employeeName,job) ,branch(No,Name), Customer(customerNo,costomerName,gender), ,Invoice (employeeNo,customerNo,total price ,invoiceNo,InvoiceDate, branchNo ) InvoiceDeatail contain List Of Purchase Items contain detail information related to the invoice (invoiceNo,ItemNo, paidPrice, quantity) . create getlemTotalPrice function which to return quantity*paidPrice