Database Schema Design

Database schema design is a critical step in low-level design that involves designing the structure and organization of a database based on the entity-relationship mapping. It determines how data will be stored, how entities will be related to each other, and how queries will be executed efficiently.

When designing a database schema, it is important to consider the performance, scalability, and integrity of the database. This includes determining the appropriate data types for each attribute, defining primary and foreign key constraints, and establishing relationships between entities.

To illustrate the process of database schema design, let's continue with our payment application example. Based on the entity-relationship mapping we defined earlier, we can design the following database schema:

• User table

  • user_id (Primary key)
  • name
  • email

• Account table

  • account_id (Primary key)
  • user_id (Foreign key referencing User.user_id)
  • balance

• Transaction table

  • transaction_id (Primary key)
  • account_id (Foreign key referencing Account.account_id)
  • amount
  • timestamp

The above database schema represents the entities defined in our payment application and their relationships. It allows us to store and retrieve user information, account details, and transaction data efficiently.

In Java, we can create classes that represent the entities in our database schema. Here's an example:

1class User {
2  int user_id;
3  String name;
4  String email;
5}
6
7class Account {
8  int account_id;
9  int user_id;
10  double balance;
11}
12
13class Transaction {
14  int transaction_id;
15  int account_id;
16  double amount;
17  Date timestamp;
18}

In the main method of a Java program, we can write the logic related to database schema design, such as creating tables, defining constraints, and establishing relationships.

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class Main {

  public static void main(String[] args) {

    // Replace with your Java logic

    // related to database schema design

  }

}