mybatis-plus 自带QueryWrapper自定义sql实现复杂查询

常用写法

xxxDO=实体类， 相当于: select name, id from xxx group by name where delete_flag = 0 and status = 0

LambdaQueryWrapper<xxxDO> queryWrapper = Wrappers.lambdaQuery();
    queryWrapper.select(xxxDO::getName, DO::getId);
    queryWrapper.eq(xxxDO::getDeleteFlag, 0);
    queryWrapper.eq(xxxDO::getStatus, 0);
    queryWrapper.groupBy(xxxDO::getName);
    List<xxxDO> list = getBaseMapper().selectList(queryWrapper);

自定义sql

xxxDO=实体类，相当于: select sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN 男 WHEN sex = 0 THEN 女 ELSE 未知 END AS sexStr from xxx group by sex where status = 0

LambdaQueryWrapper<xxxDO> queryWrapper = new QueryWrapper<xxxDO>()
            .select("sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN 男 WHEN sex = 0 THEN 女 ELSE 未知 END AS sexStr").lambda();
    queryWrapper.eq(xxxDO::getStatus, 0);
    queryWrapper.groupBy(xxxDO::getSex);
    List<Map<String, Object>> mapList = getBaseMapper().selectMaps(queryWrapper);
    Map<String, String> registerNumMap = new HashMap<>(mapList.size());
    for (Map<String, Object> map : mapList) {
        String key = String.valueOf(map.get("sexStr"));
        String num = String.valueOf(map.get("num"));
        registerNumMap.put(key, num);
    }

返回结果是一个list, 里面的map key是查询的属性名， value是参数值。伪代码示意：

list[0]

map[0] (sex=1)

map[1] (num=5)

map[2] (sexStr=男)

list[1]

map[0] (sex=1)

map[1] (num=5)

map[2] (sexStr=男)

偶然而发， 记录一下

补充: 查询条件中使用函数apply

queryWrapper.apply("INET_ATON(qsip) <= INET_ATON({0})", ipQuery); queryWrapper.apply("INET_ATON(zzip) >= INET_ATON({0})", ipQuery);

补充: 末尾sql追加last

queryWrapper.last(" order by id asc"); queryWrapper.last("limit 1");

补充:排序

// last也可以追加limit 这里用page接口 IPage<Entity> buildPage = new Page<>(0, 200); // ServiceImpl的page调用的是baseMapper的selectPage, getBaseMapper().selectPage() IPage<Entity> page = page(buildPage, queryWrapper); sql打印