习惯用mysql的查询语句对mongodb复杂查询有时候力不从心，推荐mongodb聚合查询

db.getCollection("countTurnTableLog")
.aggregate([
                        { $match : { $and : [{date : { $gte : 20210201, $lte : 20210222 }}, {behavior : "drawLucky"}]}}, //过滤条件
                        { $group: { _id: {user_id:"$userId",date:"$date"}, count: { $sum: 1 } } }, // 分组查询
                                                {$match:{count:{$gt:1}}}, // 分组之后再过滤
                                                {$group:{_id:"$_id.date",count:{$sum:1}}}, //过滤之后再分组
                                                  {$sort: {"_id": 1} }//最后再排序
                       ]);

该段mongodb的查询就类似于

select * from (
select count(1),date from countTurnTableLog where date>=20200201 and date <=20200222 and behavior = 'drawLucky'
group by userId,date having count(1)>1) a group by a.date

需求：查询 日期再20210201 到 20210222 时间内，behavior是 drawLucky，按天每天出现两条记录的用户数

内嵌数据查询

1 对查询内嵌数组元素的条件查询:$elemMatch（条件查询所有评论中评论人是：zensss，内容是：dasdsadsadasdsad，的文档）
mongo 查询语句

db.users.find({"comments":{"$elemMatch":{"author" : "zensss","content" :"dasdsadsadasdsad"}}}) .pretty()

java查询语句

        Query query4 = new Query(Criteria.where("comments").elemMatch(Criteria.where("author").is("zensss").and("content").is("dasdsadsadasdsad")));
        mongoTemplate.find(query4,MongoUser.class,"user");

2 分页查询内嵌数组中的数据

//最新的三条数据
db.users.find({"username":"lison"},{"comments":{"$slice":[0,3]}}).pretty()
//分页查询下一页的数据
db.users.find({"username":"lison"},{"comments":{"$slice":[3,3]},"$id":1}).pretty();

java查询语句

//最新的三条数据
    Query query1 = new Query(Criteria.where("username").is("sean"));
        query1.fields().include("comments").slice("comments",0,3);
        mongoTemplate.find(query1,MongoUser.class,"user");
//分页查询下一页的数据
   Query query3 = new Query(Criteria.where("username").is("lison"));
        query3.fields().include("comments").slice("comments",3,3).include("id");
        mongoTemplate.find(query3,MongoUser.class,"user");