Getting Started with MongoDB is simple (3)

# #简单的mongodb入门命令 # #

1.show dbs; View Current Database

2.use DatabaseName; Select Library

3.show tables/collections; See which tables are in the database

4.db.help (); View some of the operations commands for database

5.mongodb Library is created implicitly , we can use a non-existent library, and then create collection under the library, you can create the library;

For example: db.createcollection (' user ');
Db.user.insert ({id:10, Name: ' Wangwu ', age:20});
Db.user.find ();

6.collection allows implicit creation:
Db.collectonName.insert (document);

7. Delete collction;
Db.collectionName.drop ();

8. Delete database;
Db.dropdatabase ();

# #mongodb基本操作 # #

1. Add: Insert

Db.stu.insert ({stu_id: ' 001 ', Name: ' Xiaoqiang '});
Create multiple documents at once: JSON is an object, JS has the concept of arrays, we just need to put more than one object into an array can be;

For example:
Db.stu.insert ([{_id:3, SN: ' 003 ', Name: ' Liuqiang '},{sn: ' 006 ', Name: ' Zhaoming '}]);
We can write in any depth;

2. Delete: Remove

Syntax : db.collection.remove (query expression, options);
The option refers to whether (Just_one_line:true/false) deletes only one row, and the default is false;

For example:
Db.stu.remove ({sn: ' 001 '}); Remove the student with SN 001 in St Table
Db.stu.remove ({sn: ' 001 ', true}); Delete Only one row

Attention:
1) The query expression is still a JSON object;
2) The rows of the query expression matching will be deleted;
3) If the query expression is not written, all the documents in the collection will be erased;

3. Change: Update

Syntax : db.collection.update (query expression, assignment expression, new option);
Who to change--query expression
change to what--assignment expression
action option--optional parameter

For example:
Db.stu.update ({name: ' Dalang '}, {name: ' Zhagnqiang '}),     //New document replaces the old document directly
Db.stu.update ({name: ' Liuwei '}, {$set: {name: ' Yaoming '}});       //change only one column

An assignment expression when modified:
$set Modify the value of a column
$unset Delete a column
$rename Rename a column
$inc Grow a column
$setOnInsert The fields that can be supplemented when upsert is true and an insert operation has occurred;

Exp:

Db.stu.insert ({name: ' Zhangqiang ', Age16,sex: ' m ', weight:60});

Db.stu.update ({$set: {Name:wangli}, $unset: {age:17}, $rename: {sex: ' Gender '}, $inc: {weight:2}});

 
optional parameter:
  {upsert:false  multi:false}
  upsert: No matching rows are inserted directly into the row (if a field is queried to modify, otherwise new information is added)
   Muiti: Modify multiple rows (even if the query expression hits more than one line, and if you want to change multiple rows, add this option)
  
Exp:

Db.stu.update ({name: ' Zhangqiang '}, $set: {name: ' Lisi '},{upsert:true});

Db.stu.update ({name: ' Zhangqiang '}, $set: {name: ' Lisi ', $setOnInsert: {high:180}},{upsert:true});       //plus the High property

Db.stu.update ({gender: ' m '}, $set: {genter: ' Men '},{multi:true});

4. Check: Find,findone

Db.stu.find (); Querying all the Documents

Db.stu.find ({age:18}); Querying the columns of the age property in all documents

Db.stu.find ({}, {age:20}); Query age=20 columns in all documents without querying the ID attribute

Db.stu.find ({name: ' Zhngsan '}, {age:1,_id:0}); Find out that name is Zhangsan's age.

Getting Started with MongoDB is simple (3)