In our daily life, we may not be aware of the frequently used database systems. Before formally learning the database, let's take you to understand the common database system applications around you.
When reading the following content, readers can first think of:
database as a set of related data
database management system (DBMS) as the software that manages and controls this set of
data Everything in ,
more precise definitions of these terms are given later in this chapter.
The following are some common database applications in life.
Shopping in a supermarket
When we buy something in a supermarket, we are accessing a database.
At checkout, cashiers use barcode readers to scan each item a customer purchases. This barcode reader is connected to an application that accesses the commodity database. The program finds out the price of the commodity from the commodity database based on the barcode, then subtracts the quantity of this commodity from the inventory, and displays the corresponding price on the screen. .
If the inventory is lower than the set critical value, the database system will prompt purchase to supplement the inventory. If a customer calls the supermarket to order an item, the salesperson can run the application to check whether there is enough stock for this item in the database.
Credit card consumption
When using a credit card to purchase goods, the salesperson checks whether the customer has sufficient credit limit. This check can be done by phone or automatically by a credit card reader linked to the computer system. Either way, there must be a database somewhere that holds all the information about the customer's credit card purchases.
In order to check the customer's credit status, a database application is needed. Using the credit card number, you can find out the total price of the goods purchased by the customer this month, plus the price of the product you want to buy with the credit card this time, and judge whether it is still within the credit limit. Inside. And, if the user confirms the purchase, the detailed content of the purchased product will be recorded in the database.
The application also accesses a database to check that the credit card is not stolen or lost before agreeing to the purchase. In addition, there are generally some other applications responsible for sending credit card usage records to credit card holders every month, and sending information to credit card holders after payment is received.
Travel agency booking vacation itinerary
When a traveler asks a travel agency about a vacation itinerary, the travel agency accesses multiple databases that contain holiday and flight details.
If a customer books a trip, the database system must make all the necessary booking arrangements. In this case, the system must ensure that a seat is not booked by two different travel agencies and that the reserved seats for the flight do not exceed the fixed seats for the flight.
For example, assuming there is only the last seat left on the flight from Qinghai to Beijing, but two travel agencies request to reserve this seat at the same time, the system must be able to distinguish and handle this situation, that is, allow one reservation to continue, and notify the other travel agency that it has been booked. There are no seats left. Travel agencies often may have another database for listing tickets.
Library
In a library there may be a database that stores details of all books in the library, details of patrons, etc.
The database system can also provide reservation service, which allows readers to reserve books, and when the book can be borrowed, the reader will be notified by email or other means. The system can also send reminders to readers who have borrowed books, informing them that they have not returned the borrowed books within the specified time limit.
In addition, all libraries are now equipped with a computer indexing system, which realizes the automatic query of books. Using this system, readers can find out the location of the book they want to borrow and whether it has been borrowed by querying information such as the title, author or publication year.
Buying Insurance
Whenever looking to purchase a policy, such as life, homeowners, or auto insurance, an insurance broker accesses the databases of multiple insurance agencies.
The database system will determine the amount of insurance based on the customer's personal details provided, such as name, home address, age, etc. Insurance brokers can search multiple databases to find a policy that will give their clients the best deal.
Online shopping
The shopping websites we usually use are all driven by database applications, for example, Taobao, Jingdong, Dangdang, etc.
There are many online bookstores out there, which allow customers to browse and buy books in different categories such as computer or management. You can also browse books by author name. In any case, a database exists on the organization's web server containing details of all books (title, author, price, sales history, publisher, synopsis and long description, etc.), availability, shipping, etc. status, availability and ordering information.
Books can be cross-referenced in the database. For example, a book might be listed under multiple categories, such as Computers, Programming Languages, Bestsellers, and Recommended Books.
We can buy one or more books online. Dangdang.com will save previous transaction records (historical orders) in the database, including detailed information such as titles of books purchased, delivery addresses and payment prices, to provide personalized services for website users.
University
If you are studying at a university, the school will have a database system (student management system) to store all information about students, including registered courses, various scholarships obtained, courses selected in previous years and courses being selected this year, and exams grade information etc. There may also be a database storing details of staff working at the university.
The above are the applications of common databases in life, and you will definitely encounter more other database systems. Although we are familiar with these applications today, database systems are actually quite complex technologies that have been developed for more than 60 years.
