Detailed explanation of writing greater than or equal to in MyBatis

MyBatis is a popular Java persistence layer framework that is widely used in various Java projects. When using MyBatis for database operations, you often encounter situations where you need to query a value greater than or equal to a certain value. This article will introduce in detail how to implement the greater than or equal query in MyBatis and provide specific code examples.

First, let us take an actual demand scenario as an example: Suppose we have a data table named User, containing the fields id and age, and we need to query all users whose age is greater than or equal to 18 years old. Next, we will introduce how to use MyBatis to implement this query requirement.

Step one: Write the User entity class

First, we need to create a User entity class to map the User table structure in the database. The code is as follows:

public class User {
    private Long id;
    private Integer age;
    
    // 省略 getter 和 setter 方法
}

Step 2: Write the Mapper interface and Mapper XML file

Next, we need to write the Mapper interface and the corresponding Mapper XML file to define the query method and SQL statement. Add the following method to the Mapper interface:

public interface UserMapper {
    List<User> selectUsersByAgeGreaterThanEqual(@Param("age") Integer age);
}

In the Mapper XML file, define the corresponding SQL statement:

<select id="selectUsersByAgeGreaterThanEqual" parameterType="java.lang.Integer" resultType="User">
    SELECT id, age
    FROM User
    WHERE age >= #{age}
</select>

Step 3: Call the Mapper method for query

Finally , we call the Mapper method in the business logic to query. The sample code is as follows:

public class UserService {
    
    @Autowired
    private UserMapper userMapper;
    
    public List<User> getUsersByAgeGreaterThanEqual(Integer age) {
        return userMapper.selectUsersByAgeGreaterThanEqual(age);
    }
}

This completes all the steps to implement the greater than or equal query in MyBatis. Through the above example, we can clearly see how to use MyBatis to perform a greater than or equal query, and understand the specific code implementation of each step. Hope this article is helpful to you!

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