//1、查询所有,不加条件去查询userMapper.selectList(null).forEach(System.out::println);       //forEach遍历打印

//2、查询所有,加条件去查询            //2.1、new QueryWrapper        QueryWrapper queryWrapper1 = new QueryWrapper();            //2.2、设置条件        queryWrapper1.eq("age", 20);          userMapper.selectList(queryWrapper1).forEach(System.out::println);

QueryWrapper queryWrapper2 = new QueryWrapper();           //3.1、设置多条件           Map<String,Object> map = new HashMap<>();           map.put("age",20);           map.put("name","张三");           //3.2、map放进queryWrapper        queryWrapper2.allEq(map);

//4、分页查询        //1、配置类paginationInterceptor        //2、设置分页参数        Page<User> page = new Page<>(1,3);      //当前页，每页显示条数2        Page<User> userPage = userMapper.selectPage(page, null);//分页参数，查询条件
        System.out.println(userPage.getCurrent());      //当前页        System.out.println(userPage.getSize());     //每页显示条数
        userPage.getRecords().forEach(System.out::println);     //查询结果

@Test    void select() {        //1、查询所有,不加条件去查询        userMapper.selectList(null).forEach(System.out::println);       //forEach遍历打印
        //2、查询所有,加条件去查询            //2.1、new QueryWrapper        QueryWrapper queryWrapper1 = new QueryWrapper();            //2.2、设置条件        queryWrapper1.eq("age", 20);        /**         * lt           #小于         * gt       #大于         * ne       #不等于         * eq       #等于         * le           #小于等于         * ge       #大于等于         * between      #between         * like like    模糊查询        #likeLeft 左模糊  likeRight 右模糊         * isNull         * isNotNull         * in                         #inSql in sql语句         * notIn         * orderBy                  #排序 ASC DESC 升序降序         * orderByDesc         */        userMapper.selectList(queryWrapper1).forEach(System.out::println);
        //3、多条件去查询        QueryWrapper queryWrapper2 = new QueryWrapper();            //3.1、设置多条件            Map<String,Object> map = new HashMap<>();            map.put("age",20);            map.put("name","张三");            //3.2、map放进queryWrapper        queryWrapper2.allEq(map);
        //byId        User user = userMapper.selectById(1);        System.out.println(user);
        //byBatchIds        userMapper.selectBatchIds(Arrays.asList(1,2,3)).forEach(System.out::println);       //Arrays.asList(1,2,3)是一个数组，把数组转换成list集合
        //通过map条件查询        //map只能是一个条件，不能是多个条件        Map<String,Object> map1 = new HashMap<>();        map1.put("age",20);        map1.put("name","张三");        userMapper.selectByMap(map).forEach(System.out::println);
        //4、分组查询        QueryWrapper queryWrapper3 = new QueryWrapper();        queryWrapper3.gt("age",20);        System.out.println(userMapper.selectCount(queryWrapper3));
        //将查询结果放入map中        userMapper.selectMaps(queryWrapper1).forEach(System.out::println);
        //分页查询        //1、配置类paginationInterceptor        //2、设置分页参数        Page<User> page = new Page<>(1,3);      //当前页，每页显示条数2        Page<User> userPage = userMapper.selectPage(page, null);//分页参数，查询条件
        System.out.println(userPage.getCurrent());      //当前页        System.out.println(userPage.getSize());     //每页显示条数
        userPage.getRecords().forEach(System.out::println);     //查询结果

        //封装到map中        Page<Map<String,Object>> mapPage = new Page<>(1,3);     //分页参数，查询条件        userMapper.selectMapsPage(mapPage, null).getRecords().forEach(System.out::println);     //查询结果
        //查询所有，只输出id        userMapper.selectObjs(null).forEach(System.out::println);     //查询结果
        //查询一个        System.out.println(userMapper.selectOne(null));     //查询结果
    }

    /**     * Insert     */    @Test    void insertTest(){        User user = new User();        user.setName("张三");        user.setAge(20);        userMapper.insert(user);        System.out.println(user);    }

    /**     * Delete     */    @Test    void deleteTest(){        //通过id删除        userMapper.deleteById(1);
        //通过多条件id删除        userMapper.deleteBatchIds(Arrays.asList(1,2,3));
        //通过条件删除        QueryWrapper queryWrapper = new QueryWrapper ();        queryWrapper.eq("name","张三");       //与查询相同        userMapper.delete(queryWrapper);
        //通过条件删除---Map        Map<String,Object> map = new HashMap<>();        map.put("name","张三");        userMapper.deleteByMap(map);
    }

   /**     * Update     */    @Test    void updateTest(){
        //通过id更新        User user = userMapper.selectById(1);       //查询数据        user.setName("李四");     //修改数据        user.setAge(30);        userMapper.updateById(user);
        //通过QueryWrapper更新        User user1 = userMapper.selectById(1);      //查询数据        QueryWrapper queryWrapper = new QueryWrapper();         //构建条件        queryWrapper.eq("name","张三");        queryWrapper.eq("age",20);        userMapper.update(user1,queryWrapper);     //更新数据
    }

package com.southwind.mybatisplus.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;import com.southwind.mybatisplus.entity.ProductVO;import com.southwind.mybatisplus.entity.User;import org.apache.ibatis.annotations.Select;
import java.util.List;
public interface UserMapper extends BaseMapper<User> {    @Select("select p.*,u.name userName from product p,user u where p.user_id = u.id and u.id = #{id}")    List<ProductVO> productList(Integer id);}