NDB is the newest way to store data in GAE(Google AppEngine). I had to struggle with it to get a good start here is what i learned from my experiments.
Note: this tutorial is for GAE using Python.

Here tables are represented by class and class name represents table(kind).
These class has to inherit form ndb.Model.

for this.
here is the code

create file with the two kinds

from google.appengine.ext import ndb
class Religion(ndb.Model):
    religion = ndb.StringProperty(required=True)
    no_of_people = ndb.IntegerProperty()
    name = ndb.StringProperty()
 
class Student(ndb.Model):
    name = ndb.StringProperty()
    age = ndb.StringProperty()
    religion = ndb.StringProperty()
Save this file named as models.py .

In the above example, we have to declare entity property(like column in mysql) and data type or property
e.g. ndb.StringProrperty(required=True)

There are more type, follow the link for this.
Like i have passed the option that this property can't be empty  using required = True.

There are more for this follow the link. These called property options.

Note: These property can be accessed by shorter name.
e.g
first_name_student = ndb.StringProperty('f_name')
Now, the property can be accessed using f_name too.

Note: The link has advanced part you can skip for now link.

Put data into the table(ndb.Model).
case 1
        student_key = ndb.Key(Religion,"brotherhood")
        student = Student(parent = student_key)
        student.age = age
        student.id = "Global"
        student.religion = "brotherhood"
        student.name = "human"
        student.put() #this is put data into the entity table.
Here i have used parent key that links it the entity in the kind Religion with id="brotherhood".

There is no need to put parent key you can do this directly
case 2
       student = Student(parent = student_key)
        student.age = age
        student.id = "Global"
        student.religion = "brotherhood"
        student.name = "human"
        student.put() #this is put data into the entity table.
Get entity:
you can get the entity in
case 2:
As
entity = Student.get_by_id(id_value)
not id_value can be get as  key = student.put(); id_value = key.id() # this gives the id.

for the case 1:
entity_value = Student.get_by_id(id_value, parent=ndb.Key(models.Religion,"brotherhood")
If have used  parent key then we have to supply the parent key to get the entity.

Alternate:
key = student.put()
id = key.id()
parent_key = key.parent()
Get the parent entity.
        self.response.out.write("=======####-----------<br/>")
        self.response.out.write(key.parent().id())
        self.response.out.write("<br/>")
        self.response.out.write(key.parent().urlsafe())
        self.response.out.write("<br/>")
        self.response.out.write(key.parent())
        self.response.out.write("<br/>")
        self.response.out.write(key.parent().get())
        
For more on the url_safe. follow the link.

For Google cheat sheet.follow the link



google.appengine.ext.db
ndb.model
q = MyModel.all()
q.ancestor(ancestor_key)
q =
 MyModel.query(ancestor=ancestor_key)
q = MyModel.all(keys_only=True)
r = q.fetch(N)
r = MyModel.query() \
   .fetch(N, keys_only=True)
# Alternatively:
q = MyModel.query(
     default_options=QueryOptions(
                     keys_only=True))
r = q.fetch(N)

For the cursor and pagination use the following . here form the same cheat sheet.

Cursors

q = MyModel.all()
a = q.fetch(20)
cur = q.cursor()
q = MyModel.query()
a, cur, more = q.fetch_page(20)
# (1)
q.with_cursor(cur)
b = q.fetch(20)
b, cur, more = \
 q.fetch_page(20, start_cursor=cur)
q.with_cursor(end_cursor=cur)
b = q.fetch(20)
q.fetch(20, end_cursor=cur)



 a= holds the data here and
cur = cursor for the next data
more = true if more data is there.

Note: for the next data and cursor : use
start_cursor = cur
for the previous data and cursors
end_cursor = cur

list_of_keys = ndb.put_multi(list_of_entities)
list_of_entities = ndb.get_multi(list_of_keys)
ndb.delete_multi(list_of_keys)

For, now this is ok! next we will look into the id's some link.
from google.appengine.api import namespace_manager

namespace_manager.set_namespace('thenamespace')
MyModel.get_by_id(some_id_name)
http://stackoverflow.com/questions/10321244/cant-use-ndb-get-by-id-to-get-entity-in-namespace