在使用MyBatis-Plus时，我们可以通过QueryWrapper来构建复杂的查询条件，其中可以使用and和or来嵌套条件。以下是一个使用and和or嵌套条件的例子：
1. and ( ... or ... or...) 格式
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.IService;// 假设有一个实体类Entity和对应的服务类IService
public class Entity {private Integer id;private String name;private Integer age;// 省略其他字段、构造函数、getter和setter方法
}public interface IEntityService extends IService<Entity> {// 其他业务方法
}// 使用QueryWrapper构建查询条件
QueryWrapper<Entity> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("name", "Alice") // 外层and条件.and(i -> i.eq("age", 25).or().eq("age", 30)); // 嵌套and条件，其中包含or条件// 使用服务类进行查询
List<Entity> result = entityService.list(queryWrapper);@GetMapping(value = "/list")public Result<IPage<YwglInfo>> queryPageList(YwglInfo ywglInfo,@RequestParam(name = "pageNo", defaultValue = "1") Integer pageNo,@RequestParam(name = "pageSize", defaultValue = "10") Integer pageSize,HttpServletRequest req) {QueryWrapper<YwglInfo> queryWrapper = QueryGenerator.initQueryWrapper(ywglInfo, req.getParameterMap());String kh = req.getParameter("kh");if (StringUtils.isNotEmpty(kh)){//原来bug sql//queryWrapper.eq("send_addr",kh).or().eq("receive_addr",kh);queryWrapper.and(wrapper -> wrapper.eq("send_addr",kh).or().eq("receive_addr",kh));}Page<YwglInfo> page = new Page<YwglInfo>(pageNo, pageSize);IPage<YwglInfo> pageList = ywglInfoService.page(page, queryWrapper);return Result.OK(pageList);}打印出来的正确SQL如下
send_type = '0'并且(send_addr = '4224' 或者 receive_addr = '4214')
SELECT send_addr, send_type, receive_addr, receive_type,create_time, create_by, state_desc, comm_type, sfsc, send_time
FROM ywglinfo WHERE(send_type = '0' AND (send_addr = '4224' OR receive_addr = '4214'))
ORDER BY create_time DESC错误SQL少了括号
send_type = '0'并且send_addr = '4224' 或者 receive_addr = '4214'
SELECT send_addr, send_type, receive_addr, receive_type,create_time, create_by, state_desc, comm_type, sfsc, send_time
FROM ywglinfo WHERE
(send_type = '0' AND send_addr = '4224' OR receive_addr = '4214')
ORDER BY create_time DESC2. or ( ... and ... and ...) 格式
年纪既不等于6也不等于33
wrapper.or(wrapper -> wrapper.ne("age", 6).ne("age",33);
)
)
)
