MongoDB CRUD之R

Posted 2020-10-24 onetoinf

文档查询

命令	操作
db.mycoll.find(key:value)	查询符条件的数据
db.mycoll.find(...).count()	查询并计数
db.mycoll.find(...).limit(n)	限制查询条数
db.mycoll.find(...).skip(n)	跳过查询
db.mycoll.find(...).sort(...)	查询并排序
db.mycoll.find(...).pretty()	查询并优化输出结果

Read

查看所有

25 > db.set2test.find()
{ "_id" : ObjectId("5a7943273fdd5fec85460638"), "x" : 3 }
{ "_id" : ObjectId("5a7943273fdd5fec85460639"), "x" : 4 }
{ "_id" : ObjectId("5a7943273fdd5fec8546063a"), "x" : 5 }
.......
{ "_id" : ObjectId("5a7943273fdd5fec8546064b"), "x" : 22 }
Type "it" for more
26 > it
{ "_id" : ObjectId("5a7943273fdd5fec8546064c"), "x" : 23 }
{ "_id" : ObjectId("5a7943273fdd5fec8546064d"), "x" : 24 }
{ "_id" : ObjectId("5a7943273fdd5fec8546064e"), "x" : 25 }

输入it查看更多数据

指定字段

44 > db.unicorns.find({},{_id: 0, name: 1, gender: 1, weight: 1})
{ "name" : "Aurora", "gender" : "f", "weight" : 450 }
{ "name" : "Horny", "weight" : 600, "gender" : "m" }
{ "name" : "Aurora", "weight" : 450, "gender" : "f" }
{ "name" : "Unicrom", "weight" : 984, "gender" : "m" }
{ "name" : "Roooooodles", "weight" : 575, "gender" : "m" }
{ "name" : "Solnara", "weight" : 550, "gender" : "f" }
{ "name" : "Ayna", "weight" : 733, "gender" : "f" }
{ "name" : "Kenny", "weight" : 690, "gender" : "m" }
{ "name" : "Raleigh", "weight" : 421, "gender" : "m" }
{ "name" : "Leia", "weight" : 601, "gender" : "f" }
{ "name" : "Pilot", "weight" : 650, "gender" : "m" }
{ "name" : "Nimue", "weight" : 540, "gender" : "f" }
{ "name" : "Dunx", "weight" : 704, "gender" : "m" }

条件查询

45 > db.unicorns.find({weight: {$gt: 700}},{_id: 0, name: 1, gender: 1, weight: 1})
{ "name" : "Unicrom", "weight" : 984, "gender" : "m" }
{ "name" : "Ayna", "weight" : 733, "gender" : "f" }
{ "name" : "Dunx", "weight" : 704, "gender" : "m" }

大小

操作符	意义	符号
$gt	greater than	>
$gte	gt equal	>=
$lt	less than	<
$lte	lt equal	<=
$ne	not equal	!=
$eq	equal	=

41 > db.unicorns.find({weight: {$gt: 700}}).count()
3

逻辑

操作符	意义	符号
$or	or	||
$and	and	&&

48 > db.unicorns.find(
{
    $and: 
    [{weight: {$gt: 700}},{gender: 'f'}]
    }, 
{
    _id: 0, 
    name: 1, 
    gender: 1, weight: 1
    }
)
{ "name" : "Ayna", "weight" : 733, "gender" : "f" }
49 > 

等价于

49 > db.unicorns.find(
    {
        weight: {$gt: 700},gender: 'f'
        }, 
    {
        _id: 0, name: 1, gender: 1, weight: 1
        }
)
{ "name" : "Ayna", "weight" : 733, "gender" : "f" }

模糊

• 正则

54 > db.unicorns.find({name: {$regex: /^[A-D]/}}, {_id: 0, name: 1})
{ "name" : "Aurora" }
{ "name" : "Aurora" }
{ "name" : "Ayna" }
{ "name" : "Dunx" }

• 键值存在与否

61 > db.unicorns.find({ loves: { $exists: false } }, {_id: 0})
{ "name" : "Aurora", "gender" : "f", "weight" : 450 }

• 范围

64 > db.unicorns.find({ name: { $in: ["Ayna", "Aurora"] } }, {_id: 0, name: 1, gender: 1, weight: 1})
{ "name" : "Aurora", "gender" : "f", "weight" : 450 }
{ "name" : "Aurora", "weight" : 450, "gender" : "f" }
{ "name" : "Ayna", "weight" : 733, "gender" : "f" }

类似的还有$nin

更多的查询操作符看这里

输出优化

28 > db.unicorns.find({gender:'f'}).pretty()
{
    "_id" : ObjectId("5a793d993fdd5fec8546062b"),
    "name" : "Aurora",
    "gender" : "f",
    "weight" : 450
}
{
    "_id" : ObjectId("5a79408c3fdd5fec8546062d"),
    "name" : "Aurora",
    "dob" : ISODate("1991-01-24T05:00:00Z"),
    "loves" : [
        "carrot",
        "grape"
    ],
    "weight" : 450,
    "gender" : "f",
    "vampires" : 43
}
......

排序

升序

30 > db.unicorns.find().sort({weight:1})
{ ... "weight" : 421,... }
{ ... "weight" : 450 }
{ ... "weight" : 450, "gender" : "f", "vampires" : 43 }
{ ... "weight" : 540, "gender" : "f" }
{ ... "weight" : 550, "gender" : "f", "vampires" : 80 }
{ ... "weight" : 575, "gender" : "m", "vampires" : 99 }
{ ... "weight" : 600, "gender" : "m", "vampires" : 63 }
{ ... "weight" : 601, "gender" : "f", "vampires" : 33 }
{ ... "weight" : 650, "gender" : "m", "vampires" : 54 }
{ ... "weight" : 690, "gender" : "m", "vampires" : 39 }
{ ... "weight" : 704, "gender" : "m", "vampires" : 165 }
{ ... "weight" : 733, "gender" : "f", "vampires" : 40 }
{ ... "weight" : 984, "gender" : "m", "vampires" : 182 }

降序

31 > db.unicorns.find().sort({weight:-1})
{ ... "weight" : 984, "gender" : "m", "vampires" : 182 }
{ ... "weight" : 733, "gender" : "f", "vampires" : 40 }
{ ... "weight" : 704, "gender" : "m", "vampires" : 165 }
{ ... "weight" : 690, "gender" : "m", "vampires" : 39 }
{ ... "weight" : 650, "gender" : "m", "vampires" : 54 }
{ ... "weight" : 601, "gender" : "f", "vampires" : 33 }
{ ... "weight" : 600, "gender" : "m", "vampires" : 63 }
{ ... "weight" : 575, "gender" : "m", "vampires" : 99 }
{ ... "weight" : 550, "gender" : "f", "vampires" : 80 }
{ ... "weight" : 540, "gender" : "f" }
{ ... "weight" : 450 }
{ ... "weight" : 450, "gender" : "f", "vampires" : 43 }
{ ... "weight" : 421, "gender" : "m", "vampires" : 2 }

分页查询

37 > db.unicorns.find().sort({weight:-1}).limit(2).skip(10).pretty()
{
    "_id" : ObjectId("5a793d993fdd5fec8546062b"),
    "name" : "Aurora",
    "gender" : "f",
    "weight" : 450
}
{
    "_id" : ObjectId("5a79408c3fdd5fec8546062d"),
    "name" : "Aurora",
    "dob" : ISODate("1991-01-24T05:00:00Z"),
    "loves" : [
        "carrot",
        "grape"
    ],
    "weight" : 450,
    "gender" : "f",
    "vampires" : 43
}

计数

39 > db.unicorns.find({gender: 'f'}).count()
6

去重

67 > db.unicorns.distinct("gender")
[ "f", "m" ]