MybatisPlus的各種查詢方法

合並轉載於https://my.oschina.net/u/241218/blog/1838534/和https://my.oschina.net/u/2427561/blog/3114039，並對原文進行了部分勘誤，在此對原作者表示感謝。

QueryWrapper 與UpdateWrapper 共有方法

方法名	說明
allEq	基於 map 內容等於=
eq	等於 =
ne	不等於 <>
gt	大於 >
ge	大於等於 >=
lt	小於 <
le	小於等於 <=
between	BETWEEN 條件語句
notBetween	NOT BETWEEN 條件語句
like	LIKE '%值%''
notLike	NOT LIKE '%值%'
likeLeft	LIKE '%值'
likeRight	LIKE '值%'
--------	--------
isNull	NULL 值查詢
isNotNull	NOT NULL 值查詢
in	IN 查詢
notIn	NOT IN 查詢
inSql	IN 查詢(sql注入式)
notInSql	NOT IN 查詢(sql注入式)
groupBy	分組 GROUP BY
orderByAsc	ASC 排序 ORDER BY
orderByDesc	DESC 排序 ORDER BY
orderBy	排序 ORDER BY
having	HAVING 關鍵詞(sql注入式)
--------	--------
or	or 拼接
apply	拼接自定義內容(sql注入式)
last	拼接在最后(sql注入式)
exists	EXISTS 條件語句(sql注入式)
notExists	NOT EXISTS 條件語句(sql注入式)
--------	--------
and(Function)	AND (嵌套內容)
or(Function)	OR (嵌套內容)
nested(Function)	(嵌套內容)

QueryWrapper 特有方法

方法名	說明
select	SQL 查詢字段內容,例如:id,name,age(重復設置以最后一次為准)

UpdateWrapper 特有方法

方法名	說明
set	SQL SET 字段(一個字段使用一次)

實例

package com.xiao.permission_system;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.additional.query.impl.LambdaQueryChainWrapper;
import com.mysql.cj.util.StringUtils;
import com.xiao.permission_system.entity.UserInfo;
import com.xiao.permission_system.mapper.UserInfoMapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;;

@RunWith(SpringRunner.class)
@SpringBootTest
public class PermissionSystemApplicationTests {

    @Test
    public void contextLoads() {
    }

    @Autowired
    private UserInfoMapper userInfoMapper;

    /**
     * 普通查詢
     */
    @Test
    public void selectById() {
        UserInfo userInfo = userInfoMapper.selectById(123);
        System.out.println(userInfo);
    }

    /**
     * 批量查詢
     */
    @Test
    public void selectByIds() {
        List<Long> ids = Arrays.asList(123L,124L,125L);
        List<UserInfo> userInfo = userInfoMapper.selectBatchIds(ids);
        System.out.println(userInfo);
    }

    /**
     * 名字包含娟並且年齡小雨30
     */
    @Test
    public void selectByWrapper() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("username","娟").lt("age",30);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }
    /**
     * 名字包含娟並且年齡大雨等於20且小於等於40並且email不為空
     */
    @Test
    public void selectByWrapper2() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("username","娟").between("age",20,30).isNotNull("email");
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 名字姓肖或者年量大雨等於20，按照年齡降序排列，年齡相同按照id生序排列
     */
    @Test
    public void selectByWrapper3() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.likeRight("username","肖")
                .or().ge("age",20).orderByDesc("age").orderByAsc("id");
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 創建日期為2019年10月2日並且直屬上級名字為王姓
     */
    @Test
    public void selectByWrapper4() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.apply("date_format(create_time,'%Y-%m-%d')={0}","2019-10-07")
                .inSql("parent_id","select id from user where username like '王%'");
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 名字為王姓並且（年齡小於40或郵箱不為空）
     */
    @Test
    public void selectByWrapper5() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        //注意：這里的or在and里面
        //參考：https://blog.csdn.net/u011229848/article/details/81902398?utm_source=blogxgwz3
        queryWrapper.likeRight("username","王")
                .and(wq->wq.lt("age",40).or().isNotNull("email"));
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }
    /**
     * 名字為王姓並且（年齡小於40並且大與20或郵箱不為空）
     */
    @Test
    public void selectByWrapper6() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.likeRight("username","王")
                .and(wq->wq.lt("age",40).gt("age",20).or().isNotNull("email"));
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }
    /**
     * 年齡23，30，40
     */
    @Test
    public void selectByWrapper8() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.in("age",Arrays.asList(20,30,40));
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }
    /**
     * 只返回滿足條件的第一條語句即可, 用last拼接limit部分
     */
    @Test
    public void selectByWrapper9() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.in("age",Arrays.asList(20,30,40)).last("limit 1");
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 名字中包含雨並且年齡小於40(只取id,username)
     */
    @Test
    public void selectByWrapper10() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.select("id","username").like("username","雨").lt("age",40);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 名字中包含雨並且年齡小於40(不取create_time,parent_id兩個字段,即不列出全部字段)
     */
    @Test
    public void selectByWrapper11() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("username","雨").lt("age",40)
                    .select(UserInfo.class,info->!info.getColumn().equals("create_time")&&
                            !info.getColumn().equals("parent_id"));
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 名字為王姓和郵箱不為空，先判斷條件是否滿足
     */
    public void testCondition() {
        String username = "王";
        String email = "";
        condition(username,email);
    }

    private void condition(String username,String email){
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.likeRight(StringUtils.isNotBlank(username),"name",username)
                    .like(StringUtils.isNotBlank(email),"email",email);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 實體作為條件構造器方法的參數
     */
    @Test
    public void selectByWrapperEntity() {
        UserInfo whereUser = new UserInfo();
        whereUser.setUsername("xiaojuan");
        whereUser.setAge(22);
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>(whereUser);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }
    /**
     * AllEq用法
     */
    @Test
    public void selectByWrapperAllEq() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        Map<String, Object> params = new HashMap<String, Object>();
        params.put("nuserame","xiaojuan");
        params.put("age",null);
        queryWrapper.allEq(params);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * AllEq用法(排除不是條件的字段)
     */
    @Test
    public void selectByWrapperAllEq2() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        Map<String, Object> params = new HashMap<String, Object>();
        params.put("nuserame","xiaojuan");
        params.put("age",null);
        queryWrapper.allEq((k,v)->!k.equals("name"),params);
        List<UserInfo> userInfoList = userInfoMapper.selectList(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * selectMaps
     */
    @Test
    public void selectByWrapperMaps() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("name","肖").lt("age",40);
        List<Map<String,Object>> userInfoList = userInfoMapper.selectMaps(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 按照直屬上級分組，查詢每組的平均年齡，最大年齡，最小年齡。並且只取年齡總和小於500的組
     */
    @Test
    public void selectByWrapperMaps2() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.select("avg(age) avg_age","min(min) min_age","max(age) max_age")
                .groupBy("parent_id").having("sum(age)<{0}",500);
        List<Map<String,Object>> userInfoList = userInfoMapper.selectMaps(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * selectObjs
     */
    @Test
    public void selectByWrapperObjs() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.select("id","name").like("name","肖").lt("age",40);
        List<Object> userInfoList = userInfoMapper.selectObjs(queryWrapper);
        userInfoList.forEach(System.out::println);
    }

    /**
     * selectCount
     */
    @Test
    public void selectByWrapperCount() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("name","肖").lt("age",40);
        Integer count = userInfoMapper.selectCount(queryWrapper);
        System.out.println(count);
    }

    /**
     * selectOne
     */
    @Test
    public void selectByWrapperSelectOne() {
        QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<UserInfo>();
        queryWrapper.like("name","肖").lt("age",40);
        UserInfo user = userInfoMapper.selectOne(queryWrapper);
        System.out.println(user);
    }

    /**
     * 使用Lambda
     */
    @Test
    public void selectLambda() {
       // LambdaQueryWrapper<UserInfo> lambda = new QueryWrapper<UserInfo>().lambda();
        LambdaQueryWrapper<UserInfo> lambda = new LambdaQueryWrapper<UserInfo>();
        lambda.like(UserInfo::getUsername,"娟").lt(UserInfo::getAge,40);
        List<UserInfo> userInfoList = userInfoMapper.selectList(lambda);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 使用Lambda,名字為王姓且（年齡小於40或郵箱不為空）
     */
    @Test
    public void selectLambd2() {
        LambdaQueryWrapper<UserInfo> lambda = new LambdaQueryWrapper<UserInfo>();
        lambda.like(UserInfo::getUsername,"娟")
                .and(lqw->lqw.lt(UserInfo::getAge,40).or().isNotNull(UserInfo::getEmail));
        List<UserInfo> userInfoList = userInfoMapper.selectList(lambda);
        userInfoList.forEach(System.out::println);
    }

    /**
     * 使用Lambda鏈式
     */
    @Test
    public void selectLambd3() {
        List<UserInfo> userInfoList = new LambdaQueryChainWrapper<UserInfo>(userInfoMapper)
                .like(UserInfo::getUsername,"娟").ge(UserInfo::getAge,20).list();
        userInfoList.forEach(System.out::println);
    }
}