mongodb查询

1.查询单条记录

> db.choice.findOne()

2.查询时指定查询条件

> db.choice.find({"_id":"005a38d5"})

默认{}查询全部

指定返回列

> db.choice.find({"_id":"005a38d5"},{"title":1,"results":1}){ "_id" : "005a38d5", "title" : "While some maintain that the recent proliferation of uncredited web sources will have a(n) (i)_____ effect on scholarship, others argue that the effects will be far more (ii)_____, claiming that academics are sensible enough not to (iii)_____ unattributed sources.", "results" : [  [  "1" ],  [  "1" ],  [  "0" ] ] }>

指定返回title和results属性

默认会返回_id，也可以设置不返回

> db.choice.find({"_id":"005a38d5"},{"title":1,"results":1,"_id":0}){ "title" : "While some maintain that the recent proliferation of uncredited websources will have a(n) (i)_____ effect on scholarship, others argue that the effects will be far more (ii)_____, claiming that academics are sensible enough not to (iii)_____ unattributed sources.", "results" : [  [  "1" ],  [  "1" ],  ["0" ] ] }>

3.条件查询


条件操作符
"$lt"===============>"<"
"$lte"==============>"<="
"$gt"===============>">"
"$gte"==============>">="
"$ne"==============>"!="


查询出blankCount大于等于1，小于等于2的一条记录

> db.choice.findOne({"blankCount":{$lte:2,$gte:1}},{"blankCount":1}){ "_id" : "006526ff", "blankCount" : 2 }>

4.$or或

> db.choice.findOne({$or:[{"blankCount":2},{"type":3}]})

查询出blankCount为2或者type为3的一条记录


5.$not

> db.choice.findOne({"type":{"$not":{$gt:3}}})

查询出type不大于3的一条记录

6.查询空null的记录

> db.questionSet.findOne({source:null})

设置字段为null后，字段为null或者不包含该字段的记录也会匹配。


如果不查询不存在的字段，则使用$exists:true

> db.questionSet.findOne({source:null,$exists:true})

7.查询时使用正则表达式

> db.choice.findOne({title:/^While/})

查询title以While开头的一条记录

8.数组查询

> db.questionSet.findOne({"questionIds":'6188e9fc'},{"questionIds":1}){        "_id" : "030eeeba",        "questionIds" : [                "6188e9fc",                "a380e38c",                "addff709",                "b6bc4eff",                "5095b99f",                "c8352e48",                "ecca3626",                "c31125f7"        ]}

查询数组questionIds中包含6188e9fc的记录


如果查询多个元素在数组中用$all，其中不分顺序。

> db.questionSet.findOne({"questionIds":{$all:['6188e9fc','a380e38c']}},{"questionIds":1}){        "_id" : "030eeeba",        "questionIds" : [                "6188e9fc",                "a380e38c",                "addff709",                "b6bc4eff",                "5095b99f",                "c8352e48",                "ecca3626",                "c31125f7"        ]}

精确匹配：

> db.questionSet.findOne({"questionIds":['6188e9fc','a380e38c']},{"questionIds":1})null

9.$slice操作符
取出数组中的前3条记录

> db.questionSet.findOne({},{"questionIds":{$slice:3}}){        "_id" : "030eeeba",        "catQuestionSet" : 2,        "orderNo" : 2,        "source" : 1,        "type" : 2,        "level" : 3,        "questionCount" : 10,        "questionIds" : [                "6188e9fc",                "a380e38c",                "addff709"        ]}

取出数组中的后3条记录

> db.questionSet.findOne({},{"questionIds":{$slice:-3}}){        "_id" : "030eeeba",        "catQuestionSet" : 2,        "orderNo" : 2,        "source" : 1,        "type" : 2,        "level" : 3,        "questionCount" : 10,        "questionIds" : [                "c8352e48",                "ecca3626",                "c31125f7"        ]}

10.内嵌文档查询


查询文档有两种方式，一种是完全匹查询，另一种是针对键值对查询。内嵌文档的完全匹配查询和数组的完全匹配查询一样，内嵌文档内键值对的数量，顺序都必须一致才会匹配。

完全匹配：

> db.choice.findOne({"explain":{"ccurlList":"3DC334A16B187EBF9C33DC5901307461","textExplain":"Answers"}})

键值对匹配(常用)：

> db.choice.findOne({"explain.ccurlList":"3DC334A16B187EBF9C33DC5901307461","explain.textExplain":"Answers"})

数组中单条文档进行匹配时，使用$elemMatch

> db.choice.findOne({"explain":{$elemMatch:{"ccurlList":"3DC334A16B187EBF9C33DC5901307461","textExplain":"Answers"}}})

11.$where查询
查询出blankCount和type相等的一条记录

> db.choice.findOne({$where:"this.blankCount==this.type"}){        "_id" : "005a38d5",        "blankCount" : 3,        "explain" : {                "ccurlList" : [ ]        },        "type" : 3,        "questionSetId" : "affccc14"     }