Operation case dry goods collection
Modify data
db.getSiblingDB('cqust'); var query criteria ={'sno':2019000000}; var
update criteria ={$set:{'body.weight':100,'name':' Wang Xiaowang '}}; db.students.update( query criteria , update criteria );
How to modify data ： First, we need to know where the data we need to modify is , Or in which field , We use $set：{ field ： New value }, In fact, for this, we obviously modify the array field .
Other operations
$type Operators are based on BSON Type to retrieve the matching data types in the collection , And return the result .
Using the type of field to query ：$type
First, we add the field name we need to query in the query criteria , And then there's one ：{$type:'string'}, You can also use numbers ：2
MongoDB The types that can be used in are shown in the following table
Type number remarks
Double1
String2
Object3
Array4
Binary data5
Undefined6 obsolete .
Object id7
Boolean8
Date9
Null10
Regular Expression11
JavaScript13
Symbol14
JavaScript (with scope)15
32-bit integer16
Timestamp17
64-bit integer18
Min key255Query with -1.
Max key127 db.getSiblingDB('cqust'); var
query criteria ={'body.weight':{$type:'string'}}; //2 it's fine too var
query criteria ={'body.weight':{$type:'double'}}; //1 it's fine too var Return condition ={};
db.students.find( query criteria , Return condition )
In this way, the query data will be the data type data we need
utilize math.random Generating random numbers , Finally, complete our update operation
// modify 2019000000 My height is 160-170 Random numbers within // modify 2019000000 The height property of is changed to string type var
query criteria ={'sno':2019000000}; var
update operation ={$set:{'body.height':Math.floor(Math.random()*10+160)}}
db.students.update( query criteria , update operation ); // Verify query var query criteria ={'sno':2019000000}; var
Return condition ={}; var result=db.students.findOne( query criteria , Return condition );
Update operation with array , Take out our data , And convert it to string type data , And then use it $set： Update operation
// Method 1 ： Update specified fields （ Key points ） result.body.height=String(result.body.height) var
update operation ={$set:{'body.height':result.body.height}} db.students.update( query criteria , update operation );
Review of atomic operation knowledge
$set
A key is used to update a key value , If the key does not exist, create it .
{ $set : { field : value } }
$unset
Used to delete a key .
{ $unset : { field : 1} }
$inc
$inc A value of the document can be numeric （ Only numbers that meet the requirements ） Key to increase or decrease the operation .
{ $inc : { field : value } }
$push
hold value Append to field Go inside ,field It must be an array type , If field non-existent , An array type will be added .
usage ：
{ $push : { field : value } }
$pushAll
with $push, It's just that you can append multiple values to an array field at a time .
{ $pushAll : { field : value_array } }
$pull
From array field Delete one equal to value value .
{ $pull : { field : _value } }
$addToSet
Add a value to the array , And it only increases if the value is not in the array .
$pop
Delete the first or last element of an array
{ $pop : { field : 1 } }
$rename
Modify field name
{ $rename : { old_field_name : new_field_name } }
$bit
Bit operation ,integer type
{$bit : { field : {and : 5}}}
Offset operator
> t.find() { "_id" : ObjectId("4b97e62bf1d8c7152c9ccb74"), "title" : "ABC",
"comments" : [ { "by" : "joe", "votes" : 3 }, { "by" : "jane", "votes" : 7 } ]
} > t.update( {'comments.by':'joe'}, {$inc:{'comments.$.votes':1}}, false, true
) > t.find() { "_id" : ObjectId("4b97e62bf1d8c7152c9ccb74"), "title" : "ABC",
"comments" : [ { "by" : "joe", "votes" : 4 }, { "by" : "jane", "votes" : 7 } ] }
//$exists Operator , Determine whether the field exists db.test.insert({"name":' Wang Xiaowang '})
db.test.insert({"name":' Wang Xiaowang -123','gender':' male ','age':19})
$exists：0（1） You can find out the existence of the previous fields , If so, the property is 1, If it doesn't exist, then the property is 0
// yes name field db.test.find({'name':{$exists:1}}) // nothing name field
db.test.find({'name':{$exists:0}})
$size: You can query whether the information in this field is empty
db.test.insert({myname:[1,2,3]}) // query myname Non zero information , And there's something wrong with it
db.test.find({myname:{$not:{$size:0},$exists:1}}) var cursor
=db.students.find() for(var i=0;i<10;i++) { if(cursor.hasNext())
printjson(cursor.next()) }
Print out the information we want , Sometimes our query returns a message , But we want to learn from you Python Print like that , Formatted output , This is more conducive to our understanding and intuitive view of the characteristics of the data
Grammar is similar to JavaScript The grammar of , and Python It's not the same , But logical thinking douchabduo
var query criteria = {'grade':2019,'class':1,'major':' big data '}; var cursor =
db.students.find( query criteria ); for(var i=0; i<cursor.length(); i++) { if
(cursor[i].gender==0)
print(" full name ："+cursor[i].name+"\t height ："+cursor[i].body.height+"\t Gender ： female "); };
This is the data query case of this issue , When we learned a lot of query syntax, we found that and MySQL There is a similar phenomenon , If you want to write code according to the actual scene, you must have enough grammar and proficiency !
Every word
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