MongoDB find方法

戴面具的砺锋 發表於 2019-5-23 18:03:00

源数据
<div class="cnblogs_code">
<pre>{ 　　"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
}</pre>
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<div class="cnblogs_code">
<pre>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）</pre>
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<h3>一、查询所有数据</h3>
<h4>显示所有列</h4>
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<pre>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 user\G;
select * from user; 　　　　　 </pre>
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<h4>显示指定列</h4>
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<pre>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 user\G; 　　　　　　　　　　　　　</pre>
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<h4>查询json数据二级数据</h4>
<pre> "mobile" : {
 "number" : "18874819762"
},</pre>
以上数据，要查询number=18874819762的数据
<div class="cnblogs_code">
<pre>db["user"].find({"mobile.number":"18874819762"}).pretty() # 一级.二级.三级，依次类推</pre>
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<h3>二、等于条件查询</h3>
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<pre>db["user"].find({"accountType" : 1}).pretty() select * from user where accountType=1\G;</pre>
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<h3>三、and</h3>
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<pre>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=2\G; 　　　　　　</pre>
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<h3> 四、or</h3>
<div class="cnblogs_code">
<pre>db["user"].find(
{
 '$or':[
 {"mobile.number":"18874819762"},
 {"weixin.unionId":"o1wS90vp2ENW2Vu-QTnHlcrdU5kA"}
 ]
},
{"weixin.nick":1}
).pretty() select nick from user where number='18874819762' or unionId='o1ws90vp2ENW2Vu-QTnH1crdU5kA'</pre>
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<h4>五、< <= > >= (lt lte gt gte)</h4>
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<pre>db["user"].find({'card':{$lt:5}}).pretty() # select * from user where card < 5\G;
db["user"].find({'card':{$gt:0,$lt:5}},{"card":1}).pretty() # select card from user where card > 0 and card <5\G;
db["user"].find({'card':{$lte:5}},{"card":1}).pretty() # select card from user where card <=5;\G;
db["user"].find({'card':{$gte:0,$lte:5}},{"card":1}).pretty() # select card from user where card >=0 and card <=5\G;</pre>
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<h3>六、使用in，not in (in,nin)</h3>
<div class="cnblogs_code">
<pre>db["user"].find({"uuid":{$in:[83405282,25594661]}},{"uuid":1,"card":1}).pretty() # select uuid,card from user where uuid in(83405282,25594661)\G;
db["user"].find({"authType":{$nin:[2,1]}},{"uuid":1,"card":1,"authType":1}).pretty() # select uuid,card,authType from user where authType not in(2,1)\G;</pre>
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<h3>七、匹配null</h3>
<div class="cnblogs_code">
<pre>db["user"].find({"liaobe":null},{"uuid":1,"weixin.nick":1,"liaobe":1}).pretty() # select uuid,nick,liaobe from user where liaobei is null\G;</pre>
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<h3>八、like(MongoDB支持正则表达式)</h3>
<div class="cnblogs_code">
<pre>db["user"].find({"weixin.nick":/^随梦/},{"uuid":1,"weixin.nick":1}).pretty() # select uuid,nick from user where nick like '随梦%'\G;
db["user"].find({"weixin.nick":/袋$/},{"uuid":1,"weixin.nick":1}).pretty() # select uuid,nick,from user where nick like '%袋'\G;</pre>
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<h3>九、distinct去重</h3>
<div class="cnblogs_code">
<pre>db["user"].distinct("weixin.nick",{"weixin.nick":/^随梦/}) # select distinct(nick) from user where nick like "随梦%";</pre>
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<h3>十、count统计</h3>
<div class="cnblogs_code">
<pre>db["user"].find({"card":{$lt:5}}).count() # select count(*) from user where card <5;</pre>
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<div class="cnblogs_code">
<pre>db.runCommand( { distinct: "user", key: "weixin.nick", query: { card: {"$lt":5}} } ).values.length; # 先通过find查出数据，然后去重，最后统计</pre>
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<h3>十一、排序</h3>
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<pre>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。</pre>
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<div class="cnblogs_code">
<pre>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;</pre>
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<h4>十二、limit </h4>
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<pre>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。</pre>
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<div class="cnblogs_code">
<pre>db["user"].find({"card":{$gt:10,$lt:20}},{"uuid":1,"weixin.nick":1,"card":1}).sort({"card":1}).limit(5)</pre>
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MongoDB find方法