mongo初了解

http://try.mongodb.org/

大家可以去上面这个地址实际操作下。
JavaScript Shell
The first thing to notice is that the MongoDB shell is JavaScript-based.
So you can do things like:
  a = 5;
  a * 10;
  for(i=0; i<10; i++) { print('hello'); };

2. Documents
MongoDB is a document database. This means that we store data as documents,
which are similar to JavaScript objects. Here below are a few sample JS objects:
  var a = {age: 25};
  var n = {name: 'Ed', languages: ['c', 'ruby', 'js']};
  var student = {name: 'Jim', scores: [75, 99, 87.2]};

3. Saving
Here's how you save a document to MongoDB:
  db.scores.save({a: 99});

This says, "save the document '{a: 99}' to the 'scores' collection."
Go ahead and try it. Then, to see if the document was saved, try
  db.scores.find();

4. Saving and Querying
Try adding some documents to the scores collection:
  for(i=0; i<10; i++) { db.scores.save({a: i, exam: 5}) };

Try that, then enter
  db.scores.find();
to see if the save succeeded. Since the shell only displays 10 results at time,
you'll need to enter the 'it' command to iterate over the rest.

5. Basic Queries
You've already tried a few queries, but let's make them more specific.
How about finding all documents where a == 2:
  db.scores.find({a: 2});

Or what about documents where a > 15?
  db.scores.find({a: {'$gt': 15}});

6. Query Operators
Query Operators:
$gt is one of many special query operators. Here are few others:
  $lt  - '<',   $lte - '<=',
  $gte - '>=',  $ne  - '!='
  $in - 'is in array',  $nin - '! in array'

db.scores.find({a: {'$in': [2, 3, 4]}});
db.scores.find({a: {'$gte': 2, '$lte': 4}});

7. Updates
Now create a couple documents like these for updating:
  db.users.save({name: 'Johnny', languages: ['ruby', 'c']});
  db.users.save({name: 'Sue', languages: ['scala', 'lisp']});
Make sure they were saved by called db.users.find()
Update the first document like so:
  db.users.update({name: 'Johnny'}, {name: 'Cash', languages: ['english']});

8. Update Operators
The previous update replaced the entire document, but MongoDB also
supports partial updates to documents. For example, you can set a value:
  db.users.update({name: 'Cash'}, {'$set': {'age': 50} });
You can also push and pull items from arrays:
  db.users.update({name: 'Sue'}, {'$pull': {'languages': 'scala'} });
  db.users.update({name: 'Sue'}, {'$push': {'languages': 'ruby'} });

9. Deleting data
To delete matching documents only, add a query selector to the remove method:
  db.users.remove({name: 'Sue'});
To delete everything from a collection:
  db.scores.remove();