MongoDB first knowledge-adding and deleting changes

1. Switch database

Admin database: Use admin

Test database: Use test

2. Added:

Method One (preferred)

    c={Name="Junior", Teacher: "Xiao Zhang", stucount:    db.class. Save (c)    or Db.class. Insert (c)

Method Two

Db.class. Insert ({name: "The Junior", Teacher: "Xiao Zhang", stucount:)

Note that saving the same will prompt objectid cannot be repeated

　

3. Delete

Db.class.remove ({name: "the"})

4. Modification

Modify the Teacher field value (only one that satisfies the condition is modified)

Db.class. Update ({name: "},{$set: {name:" Teacher "," Hehhe ", Stucount:]})

Modify all that meet the criteria

Db.class. Update ({name: "},{$set: {name:" Teacher "," tt ", Stucount:}},{multi:true})

Another update is less than the new

Db.class. Update ({name: "},{$set: {name:" Teacher "," Hehhe ", Stucount:}},{upsert:true})

5. Enquiry

Without any conditions

Db.class.find ()

Query the "name=" data

Db.class.find ({name: "the"})

Querying all data for stucount>10

Db.class.find ({"Stucount", {$gt:ten})

Query the first piece of data for stucount<5

Db.class.findOne ({"Stucount": {$lt:5}})

Querying the 10>STUCOUNT>5 data

Db.class.find ({"Stucount": {$lt:ten, $gt:5}})

Paging Query

Db.class.find (). Skip.Limit (5)

How many data are queried

Db.class.find (). Count ()

How many data are queried to satisfy a condition

Db.class.find ({"Stucount", {$lt:ten}}). Count ()

The current number of queries in a paged query

Db.class.find (). Skip ((). Limit (ten). Count (true)

**count () does not write ture, is the total number

To query using cursors:

Traverse all

var cursor = Db.class.find ()  while (cursor. Hasnext ()) Printjson (cursor.  Next())

Use cursor subscript (overflow may occur)

var cursor = Db.class.find () cursor [1]

Using the array subscript

var arr=db.class.find (). ToArray () arr[1]

foreach Output

Db.class.find (). ForEach (Printjson)

It's not written in the back of the set with conditions.

MongoDB first knowledge-adding and deleting changes