MyBatis Plus 在复杂查询条件Where中加括号，多个查询条件在括号内

一、MyBatis Plus 在复杂查询条件Where中加括号，多个查询条件在括号内

使用and()方法

官方给出示例：

and(i -> i.eq("name", "李白").ne("status", "活着"))

---> sql输出结果：and (name = '李白' and status <> '活着')

二、QueryWrapper无条件时

 QueryWrapper<Demo> queryWrapper = new QueryWrapper<>();
        queryWrapper.and(query -> query.like(StringUtils.isNotBlank(demo.getName()), "demo.name", demo.getName()).or().
 like(StringUtils.isNotBlank(demo.getFrontId()), "demo.frontId", demo.getFrontId()));
 
 ------> sql输出结果:
 select id, name, frontId from demo where ( turbine.name LIKE '%测%'  OR turbine.frontId LIKE '%测%') 

三、QueryWrapper有条件时

 

 QueryWrapper<Demo> queryWrapper = new QueryWrapper<>();
 queryWrapper.eq("id",demo.getId);
queryWrapper.and(query -> query.like(StringUtils.isNotBlank(demo.getName()), "demo.name", demo.getName()).or().
like(StringUtils.isNotBlank(demo.getFrontId()), "demo.frontId", demo.getFrontId()));
 
 ------> sql输出结果:
 select id, name, frontId from demo where id = 1 and ( turbine.name LIKE '%测%'  OR turbine.frontId LIKE '%测%') 

四、理解MyBatis Plus的and()方法

• 如果QueryWrapper对象没有查询条件，则只会在where语句中添加 （）
• 如果QueryWrapper对象中有查询条件了，会在where语句中自动添加 and(查询条件)

五：基于queryWrapper实现分页查询

LambdaQueryWrapper<> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.like(StringUtils.isNoneBlank(rectificationActivityInfo.getActivityName()),RectificationActivityInfo::getActivityName,rectificationActivityInfo.getActivityName());
        queryWrapper.eq(StringUtils.isNoneBlank(rectificationActivityInfo.getStatus()),RectificationActivityInfo::getStatus,rectificationActivityInfo.getStatus());
        IPage<RectificationActivityInfo> page1 = this.page(page, queryWrapper);

 六：lambdaQueryWrapper 基于复杂sql的使用；

 LambdaQueryWrapper<CarInfo> wrapper = new LambdaQueryWrapper<>();
        wrapper.eq(CarInfo::getUsername,username);
        wrapper.and(StringUtils.isBlank(VIN),x->x.eq(CarInfo::getVinNum,VIN).or(StringUtils.isBlank(autoSN),query->query.eq(CarInfo::getMachineNum,VIN)));
        

 七、手写sql

八、mybaties的select and  or查询

 queryWrapper.eq("id", Id);
 queryWrapper.and(wrapper ->
                wrapper.eq("expire_time", 0)
                        .or()
                        .gt("expire_time",System.currentTimeMillis() / 1000)
);
 queryWrapper.select("sum(point) as point, sum(valid_points) as valid_points");

StudentDo studentDo = studentMapper.selectOne(queryWrapper);
===================================输出sql
SELECT sum(point) as point, sum(valid_points) as valid_points from student where id = "111" and (expire_time = 0 or expire_time > "2555")

 九.lambdaQueryWrapper基于select字段的查询

LambdaQueryWrapper<MdmCountry> wrapper1 = new LambdaQueryWrapper<>();
                                wrapper1.eq(MdmCountry::getCountryCode,countrycode);
                                wrapper1.select(MdmCountry::getCountryCode,MdmCountry::getCountryName,MdmCountry::getAreaId,MdmCountry::getAreaName,MdmCountry::getNationalCompanyId,MdmCountry::getNationalCompanyName);
                                List<MdmCountry> mdmCountries = mdmCountryMapper.selectList(wrapper1);