MyBatis batch query statement examples and implementation guide

Instances and code examples of MyBatis batch query statements

Introduction:
In actual development, when the amount of data is large, we often need to use batch queries to improve query efficiency. MyBatis provides good support for batch queries, which can greatly reduce the number of database accesses and improve query performance. This article will introduce examples and code examples of batch query using MyBatis.

1. What is batch query?
Batch query refers to executing multiple query statements at one time and returning multiple query results. This can reduce the number of database accesses and improve query performance.

2. Example of MyBatis batch query statement
The following is an example of a simple MyBatis batch query statement:

<!-- 定义批量查询的sql语句 -->
<select id="batchSelect" resultType="com.example.User">
    SELECT * FROM user WHERE id in
    <foreach item="item" index="index" collection="ids" open="(" close=")" separator=",">
        #{item}
    </foreach>
</select>

In the above example, we used < foreach> tag to implement batch query. <foreach>The attributes in the tag are described as follows:

1. item: The element of each iteration.
2. index: The index of each iteration.
3. collection: iterated collection.
4. open: The start tag of iteration.
5. close: The end mark of the iteration.
6. separator: The separator between iterated elements.

3. Code example using MyBatis batch query
The following is a code example using MyBatis batch query:

public List<User> batchSelect(List<Integer> ids) {
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        return userMapper.batchSelect(ids);
    }
}

In the above code example, we first obtain SqlSession object, and obtain the UserMapper object through the getMapper() method. Then call the batchSelect() method of UserMapper to perform batch query and return the query results.

4. Summary
This article introduces examples and code examples of MyBatis batch query. By using the batch query function of MyBatis, you can greatly reduce the number of database accesses and improve query performance. I hope this article will help you understand MyBatis batch query.

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