MongoDB find方法

源数据

{
　　"uuid" : 12700004,
　　"card" : 981.3000000000029,
    "weixin" : {
        "unionId" : "o1wS90l6kHDFXY2lAPDb9bPxRZxI1",
        "openId" : "o9zCJ1Aat93B0UjdlCFDAWmimBcEb",
        "nick" : "麦袋",
        "sex" : 1,
        "avatar" : "http://thirdwx.qlogo.cn/mmopen/vi_32/DYAIOgq83eoNcMa5gLGs9iaTYCmNqycSk5XUWzKDVfj6sPkk1Oia0YSy3SmMrcX3kxsvEu4UfiblckRo7CpM0xicKg/1321"
    },
    "liaobe" : null,
    "mobile" : {
        "number" : "18874819762"
    },
    "visitor" : null,
    "accountType" : 1,
    "mobileRewardReceived" : true
}

MongoDB 查询数据的语法格式如下：

db.collection.find(query, projection)

query ：可选，使用查询操作符指定查询条件
projection ：可选，使用投影操作符指定返回的键。查询时返回文档中所有键值， 只需省略该参数即可（默认省略）

一、查询所有数据

显示所有列

db["user"].find()                # MongoDB写法
db["user"].find().pretty()       # 是find出的数据在命令行中更加美观显示，不至于太紧凑，同select * from userG; 
select * from user;

显示指定列

db["user"].find({},{"liaobe":1,"mobile":1}).pretty()        # 如果projection不为空，不需要查询条件时，必须键入{}    
# projection 指定哪些列显示和不显示 (0:不显示 1:显示)

select liaobe,mobile from userG;

查询json数据二级数据

 "mobile" : {
        "number" : "18874819762"
    },

以上数据，要查询number=18874819762的数据

db["user"].find({"mobile.number":"18874819762"}).pretty()       # 一级.二级.三级，依次类推

二、等于条件查询

db["user"].find({"accountType" : 1}).pretty()   
select * from user where accountType=1G;

三、and

db["user"].find({"uuid" : 12700004,"accountType" : 1,"authType" : 2}).pretty()       # 多个条件用, 隔开
select * from user where uuid=12700004 and accountType=1 and authType=2G;

四、or

db["user"].find(
    {
        '$or':[
                {"mobile.number":"18874819762"},
                {"weixin.unionId":"o1wS90vp2ENW2Vu-QTnHlcrdU5kA"}
            ]
    },
    {"weixin.nick":1}
).pretty()

select nick from user where number='18874819762' or unionId='o1ws90vp2ENW2Vu-QTnH1crdU5kA'

五、< <= > >= (lt lte gt gte)

db["user"].find({'card':{$lt:5}}).pretty()                             # select * from user where card < 5G;
db["user"].find({'card':{$gt:0,$lt:5}},{"card":1}).pretty()            # select card from user where card > 0 and card <5G;
db["user"].find({'card':{$lte:5}},{"card":1}).pretty()                # select card from user where card <=5;G;
db["user"].find({'card':{$gte:0,$lte:5}},{"card":1}).pretty()        # select card from user where card >=0 and card <=5G;

六、使用in，not in (in,nin)

db["user"].find({"uuid":{$in:[83405282,25594661]}},{"uuid":1,"card":1}).pretty()        # select uuid,card from user where uuid in(83405282,25594661)G;
db["user"].find({"authType":{$nin:[2,1]}},{"uuid":1,"card":1,"authType":1}).pretty()    # select uuid,card,authType from user where authType not in(2,1)G;

七、匹配null

db["user"].find({"liaobe":null},{"uuid":1,"weixin.nick":1,"liaobe":1}).pretty()      # select uuid,nick,liaobe from user where liaobei is nullG;

八、like(MongoDB支持正则表达式)

db["user"].find({"weixin.nick":/^随梦/},{"uuid":1,"weixin.nick":1}).pretty()       # select uuid,nick from user where nick like '随梦%'G;
db["user"].find({"weixin.nick":/袋$/},{"uuid":1,"weixin.nick":1}).pretty()         # select uuid,nick,from user where nick like '%袋'G;

九、distinct去重

db["user"].distinct("weixin.nick",{"weixin.nick":/^随梦/})       # select distinct(nick) from user where nick like "随梦%";

十、count统计

db["user"].find({"card":{$lt:5}}).count()                      # select count(*) from user where card <5;

db.runCommand(    {       distinct: "user",       key: "weixin.nick",       query: { card: {"$lt":5}}    } ).values.length;           # 先通过find查出数据，然后去重，最后统计

十一、排序

在 MongoDB 中使用 sort() 方法对数据进行排序，sort() 方法可以通过参数指定排序的字段，并使用 1 和 -1 来指定排序的方式，其中 1 为升序排列，而 -1 是用于降序排列。

db["user"].find({"card":{$gt:10,$lt:20}},{"uuid":1,"weixin.nick":1,"card":1}).sort({"card":1})        # select uuid,nick,card from user where card>10 and card<20 asc;
db["user"].find({"card":{$gt:10,$lt:20}},{"uuid":1,"weixin.nick":1,"card":1}).sort({"card":-1})          # select uuid,nick,card from user where card>10 and card<20 desc;

十二、limit

如果你需要在MongoDB中读取指定数量的数据记录，可以使用MongoDB的Limit方法，limit()方法接受一个数字参数，该参数指定从MongoDB中读取的记录条数。

db["user"].find({"card":{$gt:10,$lt:20}},{"uuid":1,"weixin.nick":1,"card":1}).sort({"card":1}).limit(5)