Common pitfalls and solutions in MySQL table structure design: online examination system case

Common pitfalls and solutions in MySQL table structure design: Online exam system case

Introduction:
When developing database applications, optimize and design the database Table structure is crucial. A good database design can improve the performance, scalability, and stability of your application. This article will take the online examination system as an example to discuss common pitfalls in MySQL table structure design and propose solutions.

1. Trap 1: Single table design
When designing an online examination system, some developers tend to store all relevant data in one table. This design method can lead to problems such as data redundancy, difficulty in updating, and performance degradation.

Solution: Standardize the database table structure
Reasonably disperse the data into multiple tables, and carry out standardized design according to entities and relationships. For example, you can design the following tables: user table, exam table, question table, score table, etc. This can reduce data redundancy and improve data update efficiency.

2. Trap 2: Lack of indexes
Lack of indexes is one of the main reasons for low database query performance. If there are no appropriate indexes in the tables of the online exam system, queries will become very slow.

Solution: Add appropriate indexes
According to demand analysis, add appropriate indexes to the fields in the database table. For example, you can add a unique index to the user name field of the user table; you can add a joint index to the student ID field and exam ID field of the score table. This can greatly improve query efficiency.

3. Trap 3: Too many fields
When designing the database table structure of the online examination system, too many fields is also one of the common traps. Too many fields in the table not only increase data redundancy, but also affect database performance.

Solution: Reasonably split fields
Group and split the excessive fields in the table reasonably. For example, the personal information fields and account information fields in the user table are placed in two tables respectively, and related through primary and foreign key constraints. This can reduce redundancy and improve query efficiency.

4. Trap 4: Data type selection error
When designing the database table structure of the online examination system, selecting the wrong data type is also one of the common traps. Wrong data types not only lead to inaccurate data storage, but also affect database performance.

Solution: Choose the appropriate data type
Choose the appropriate data type based on the characteristics and needs of the data. For example, for the age field in the user table, you can choose the integer type; for the start time and end time fields in the exam table, you can choose the date and time type. Correct data type selection can improve the accuracy and efficiency of data storage and retrieval.

5. Trap 5: Failure to set the primary key
When designing the database table structure of the online examination system, failure to set the primary key is a common trap. Failure to set a primary key will make it difficult to ensure the uniqueness and consistency of data.

Solution: Set the appropriate primary key
Set the appropriate primary key in each table to ensure the uniqueness and consistency of the data. For example, you can set the user ID field as the primary key in the user table. Setting the primary key can improve query efficiency while ensuring data integrity and consistency.

Conclusion:
When designing the MySQL table structure, you need to avoid common traps and ensure data standardization, consistency and performance. By properly normalizing the database table structure, adding appropriate indexes, splitting fields, selecting the correct data type, and setting appropriate primary keys, the performance and stability of the online examination system can be improved.

Code example:
The following is a MySQL code example to create a user table:

CREATE TABLE `user` (
  `id` INT PRIMARY KEY AUTO_INCREMENT,
  `username` VARCHAR(50) UNIQUE NOT NULL,
  `password` VARCHAR(50) NOT NULL,
  `email` VARCHAR(50) NOT NULL,
  `age` INT,
  `gender` ENUM('男', '女', '其他'),
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  `updated_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

The above code example creates a table that contains a unique primary key, a unique username, a non-empty password, and a non-empty mailbox. , user table with age, gender, creation time and update time fields. By setting appropriate data types and constraints, data accuracy and performance are guaranteed.

References:
None

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