mybatis plus wrapper

Mybatis Plus Wrapper是Mybatis Plus框架中的一个查询条件构造器，它可以帮助我们更方便地构建复杂的查询条件。通过使用Wrapper，我们可以在不写SQL语句的情况下，实现复杂的查询操作，提高开发效率。Wrapper提供了多种查询条件的方法，如eq、ne、gt、ge、lt、le、like、in等，可以满足大部分的查询需求。同时，Wrapper还支持链式调用，可以更加灵活地构建查询条件。

相关问题

mybatis plus wrapper selectcount in用法

MyBatis Plus Wrapper 提供了很多查询条件的封装方法，其中 `in` 方法用于指定某个字段的值在一个集合中的查询。

下面是一个使用 `in` 方法进行查询的示例：

List<Integer> ids = Arrays.asList(1, 2, 3);
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.in("id", ids);
int count = userMapper.selectCount(wrapper);

上面的代码中，`ids` 是一个包含了 1、2、3 的整数集合。QueryWrapper 的 `in` 方法用于指定 `id` 字段的值在这个集合中，然后调用 `selectCount` 方法进行查询，返回的结果是符合条件的记录数。

mybatis plus querywrapper

MyBatis Plus QueryWrapper is a utility class provided by the MyBatis Plus framework to help in building complex database queries. It is used in conjunction with the MyBatis Plus Query API to construct criteria for selecting, updating, or deleting records from a database table.

QueryWrapper provides a fluent and intuitive API for constructing queries with various conditions such as equal, not equal, greater than, less than, between, like, and more. It also supports nested conditions and chaining multiple conditions together.

Here's an example of how to use QueryWrapper:

// Import the necessary classes
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.Wrapper;

// Create a QueryWrapper instance
QueryWrapper<User> queryWrapper = new QueryWrapper<>();

// Add conditions to the query
queryWrapper
    .eq("age", 25)
    .like("name", "John")
    .between("salary", 2000, 5000)
    .orderByAsc("age");

// Use the query wrapper in your MyBatis Plus query
List<User> userList = userMapper.selectList(queryWrapper);

In this example, we create a QueryWrapper instance and chain different conditions like `eq`, `like`, and `between` to construct the desired query. Finally, we pass the query wrapper to the `selectList` method of the MyBatis Plus mapper interface to execute the query.

You can find more information about QueryWrapper and other features of MyBatis Plus in their official documentation.