mongo 查詢命令

mongo之查詢

1，find命令初步使用。

    查詢某個集合中的文檔，比如查詢集合user中的文檔命令如下：

     db.user.find() 

 

 

> db.user.find()

{ "_id" : ObjectId("50900a7fdc60973b77877536"), "name" : "zhlccna", "age" : 42 }

{ "_id" : ObjectId("50900a94dc60973b77877537"), "name" : "zhlccna1", "age" : 19 }

{ "_id" : ObjectId("50900aa5dc60973b77877538"), "name" : "zhlccna2", "age" : 1 }

{ "_id" : ObjectId("509010d7eb5b2c744c6b9247"), "name" : 20, "age" : "zhlccna" }

2,查詢符文檔中某個鍵值/數值 爲特定的文檔

db.user.find({"age" : 19})

 

> db.user.find({"age" : 19})

d" : ObjectId("50900a94dc60973b77877537"), "name" : "zhlccna1", "age" : 19 }

 

 

3,指定返回值

     db.user.find({},{"age" : 1})

 

 

> db.user.find({},{"age" : 1})

{ "_id" : ObjectId("50900a7fdc60973b77877536"), "age" : 42 }

{ "_id" : ObjectId("50900a94dc60973b77877537"), "age" : 19 }

{ "_id" : ObjectId("50900aa5dc60973b77877538"), "age" : 1 }

{ "_id" : ObjectId("509010d7eb5b2c744c6b9247"), "age" : "zhlccna" }

 

 

返回user集合中所有文檔的age字段

 但是結果中會自動返回_id鍵值，如下代碼可以去除返回信息的_id鍵值

db.user.find({},{"age" : 1 ,"_id" : 0})

 

 

 

> db.user.find({},{"age" : 1 ,"_id" : 0})

{ "age" : 42 }

{ "age" : 19 }

{ "age" : 1 }

{ "age" : "zhlccna" }

 

 

4,查詢條件

$lt $lte $gt $gte $ne ,分別對應 > 、>= 、< 、<=、 =

年齡大於1小於42

db.user.find({"age"  :  {"$gt" : 1, "$lt" : 42}})

 

 

> db.user.find({"age"  :  {"$gt" : 1, "$lt" : 42}})

{ "_id" : ObjectId("50900a94dc60973b77877537"), "name" : "zhlccna1", "age" : 19 }

 

 

 

5、OR查詢

db.user.find({"$or" : [{"name" : "zhlccna"}, {"age" : 1}]})

 

> db.user.find({"$or" : [{"name" : "zhlccna"}, {"age" : 1}]})

{ "_id" : ObjectId("50900a7fdc60973b77877536"), "name" : "zhlccna", "age" : 42 }

{ "_id" : ObjectId("50900aa5dc60973b77877538"), "name" : "zhlccna2", "age" : 1 }