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
1 2 3 4 5 6 | LambdaQueryWrapper queryWrapper = Wrappers.lambdaQuery();queryWrapper.select(xxxDO::getName, DO::getId);queryWrapper.eq(xxxDO::getDeleteFlag, 0);queryWrapper.eq(xxxDO::getStatus, 0);queryWrapper.groupBy(xxxDO::getName);List 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
1 2 3 4 5 6 7 8 9 10 11 | LambdaQueryWrapper queryWrapper = new QueryWrapper() .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>> mapList = getBaseMapper().selectMaps(queryWrapper);Map registerNumMap = new HashMap(mapList.size());for (Map map : mapList) { String key = String.valueOf(map.get("sexStr")); String num = String.valueOf(map.get("num")); registerNumMap.put(key, num);}</map> |
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
1 | queryWrapper.apply("INET_ATON(qsip) = INET_ATON({0})", ipQuery); |
补充: 末尾sql追加last
1 2 | queryWrapper.last(" order by id asc");queryWrapper.last("limit 1"); |
补充:排序
1 2 3 4 5 | // last也可以追加limit 这里用page接口IPage buildPage = new Page(0, 200);// ServiceImpl的page调用的是baseMapper的selectPage, getBaseMapper().selectPage()IPage page = page(buildPage, queryWrapper); |
sql打印
补充：Mybatis-Plus QueryWrapper +sql自定义查询
一： 需要自定义的QueryWrapper查询工具类，定义查询规则
1 2 3 4 5 6 7 | public static final String SQL_RULES_COLUMN = "SQL_RULES_COLUMN";private static final String BEGIN = "_begin"; // 字段范围查询开始标识private static final String END = "_end"; // 字段范围查询结束标识private static final String STAR = "*"; // 字段模糊查询标识private static final String COMMA = ",";private static final String NOT_EQUAL = "!"; |
二： 正常的QueryWrapper查询，在mapper文件中使用 @Param(Constants.WRAPPER)
List listAll(IPage page, @Param(Constants.WRAPPER) QueryWrapper queryWrapper);
xml文件中使用ew.customSqlSegment，标签可以不加
1 2 3 | select id,lffh,xm,jsh,szrq,emlx,spzt,gjmj,flag,jlztfrom emdj${ew.customSqlSegment} |
总结
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