Các hình thức chính chuẩn bị bởi một nhân viên bán hàng là hợp đồng bán hàng, và người này chắc chắn hy vọng sẽ chuẩn bị rất nhiều trong số này! Dưới đây là những yếu tố hiện diện trên các hợp đồng bán hàng: của người mua thông tin: tên, địa chỉ, mã bưu điện, số điện thoại của đại lý thông tin: tên, | Simpo PDF Merge and Split Unregistered Version - http Chapter 4 table condition column name sample value code description N New Comparing the date column from the sale table with the start_date and end_date from the following tax_rate table we can find the exact tax rate for the date of sale table tax_rate column name sample value start_date 2006-01-01 end_date 2006-04-01 rate .075 In fact all tables should be analysed to find whether the time factor has been considered. Another example would be the color table. Assuming we are using the color codes designed by each car manufacturer does a manufacturer reuse color codes in a subsequent year for a different color If this is the case we would add a year column to the color table. Empty Columns Although empty columns are not necessarily problematic having some rows where one or many columns are empty can reveal a structural problem two tables folded into one. Let s consider the car movements. We built a structure having a car s internal number the code of the event and the moment. But what if some events need more data to be described In the paper forms we discover that when a car is washed the initials of the store assistant who did the washing appear on the form and during the interviews we learned that these initials are an important data element. In this case we can add employee information the employee code to the car_event table. This would have the benefit of enabling the system to identify which store assistant participated to any event occurring to a car leading to better quality control. Another issue that might arise is that for a specific event say washing we require more data more data like the quantity of cleaning product and the amount of time used to wash. Of those two elements one can be beneficial to improve our structure storing the start and end time of the event. But adding a column like quantity_cleaning_product to the car_event table has to be analyzed carefully. For all events
