"age" : 23,

"salary" : 15

}

4.2.4 查询记录的指定字段

[plain]

查询user集合中所有记录的name,age,salary,sex_orientation字段

> db.user.find({},{name:1,age:1,salary:1,sex_orientation:true})

{ "_id" : ObjectId("52442736d8947fb501000001"), "name" : "lfqy", "age" : 23, "salary" : 15 }

{ "_id" : ObjectId("52453cfb25e437dfea8fd4f4"), "name" : "Gal Gadot", "age" : 28, "salary" : 11000 }

{ "_id" : ObjectId("52453d8525e437dfea8fd4f5"), "name" : "Mikie Hara", "age" : 26, "salary" : 7000 }

{ "_id" : ObjectId("52453e2125e437dfea8fd4f6"), "name" : "Wentworth Earl Miller", "age" : 41, "salary" : 33000 }

{ "_id" : ObjectId("52454155d8947fb70d000000"), "name" : "not known", "sex_orientation" : "male", "age" : 13, "salary" : 30000 }

注意：这里的1表示显示此列的意思，也可以用true表示。

4.2.5 查询指定字段的数据，并去重。

[plain]

查询gender字段的数据，并去掉重复数据

> db.user.distinct('gender')

[ "male", "female" ]

4.2.6 对查询结果集的操作

[plain]

(1)Pretty Print

为了方便，mongo也提供了pretty print工具，db.collection.pretty()或者是db.collection.forEach(printjson)

> db.user.find().pretty()

{

"_id" : ObjectId("52442736d8947fb501000001"),

"name" : "lfqy",

"gender" : "male",

"age" : 23,

"salary" : 15

}

{

"_id" : ObjectId("52453cfb25e437dfea8fd4f4"),

"name" : "Gal Gadot",

"gender" : "female",

"age" : 28,

"salary" : 11000

}

{

"_id" : ObjectId("52453d8525e437dfea8fd4f5"),

"name" : "Mikie Hara",

"gender" : "female",

"age" : 26,

"salary" : 7000

}

{

"_id" : ObjectId("52453e2125e437dfea8fd4f6"),

"name" : "Wentworth Earl Miller",

"gender" : "male",

"age" : 41,

"salary" : 33000

}

{

"_id" : ObjectId("52454155d8947fb70d000000"),

"name" : "not known",

"sex_orientation" : "male",

"age" : 13

}

(2)指定结果集显示的条目

a)显示结果集中的前3条记录

> db.user.find().limit(3)

{ "_id" : ObjectId("52442736d8947fb501000001"), "name" : "lfqy", "gender" : "male", "age" : 23, "salary" : 15 }

{ "_id" : ObjectId("52453cfb25e437dfea8fd4f4"), "name" : "Gal Gadot", "gender" : "female", "age" : 28, "salary" : 11000 }

{ "_id" : ObjectId("52453d8525e437dfea8fd4f5"), "name" : "Mikie Hara", "gender" : "female", "age" : 26, "salary" : 7000 }

b)查询第1条以后的所有数据

> db.user.find().skip(1)

{ "_id" : ObjectId("52453cfb25e437dfea8fd4f4"), "name" : "Gal Gadot", "gender" : "female", "age" : 28, "salary" : 11000 }

{ "_id" : ObjectId("52453d8525e437dfea8fd4f5"), "name" : "Mikie Hara", "gender" : "female", "age" : 26, "salary" : 7000 }

{ "_id" : ObjectId("52453e2125e437dfea8fd4f6"), "name" : "Wentworth Earl Miller", "gender" : "male", "age" : 41, "salary" : 33000 }

{ "_id" : ObjectId("52454155d8947fb70d000000"), "name" : "not known", "sex_orientation" : "male", "age" : 13, "salary" : 30000 }

c)对结果集排序

升序

> db.user.find().sort({salary:1})

{ "_id" : ObjectId("52442736d8947fb501000001"), "name" : "lfqy", "gender" : "male", "age" : 23, "salary" : 15 }

{ "_id" : ObjectId("52453d8525e437dfea8fd4f5"), "name" : "Mikie Hara", "gender" : "female", "age" : 26, "salary" : 7000 }

{ "_id" : ObjectId("52453cfb25e437dfea8fd4f4"), "name" : "Gal Gadot", "gender" : "female", "age" : 28, "salary" : 11000 }