mobile website vs. mobile app

A mobile website is similar to any other website in that it consists of browser-based HTML pages that are linked together and accessed over the Internet (for mobile typically WiFi or 3G or 4G networks). The obvious characteristic that distinguishes a mobile website from a standard website is the fact that it is designed for the smaller handheld display and touch-screen interface.

Like any website, mobile websites can display text content, data, images and video. They can also access mobile-specific features such as click-to-call (to dial a phone number) or location-based mapping.

Apps are actual applications that are downloaded and installed on your mobile device, rather than being rendered within a browser. Users visit device-specific portals such as Apple’s App Store, Android Market, or Blackberry App World in order to find and download apps for a given operating system. The app may pull content and data from the Internet, in similar fashion to a website, or it may download the content so that it can be accessed without an Internet connection.

OTA: over the air update         vs manually update for mobile apps

Aaron Patterson’s talk

concur: Automated Expense Management Tools

SEO optimization: (search engine optimization)


minitest/spec ( problem? )

PG typecast — rails interacts with AR, any value fetched from non-existing column are typecasted to string

ActionController::Live ( for live data stream )

sse request





In computer software, a data access object (DAO) is an object that provides an abstract interface to some type of database or other persistence mechanism. By mapping application calls to the persistence layer, DAOs provide some specific data operations without exposing details of the database. This isolation separates the concerns of what data accesses the application needs, in terms of domain-specific objects and data types (the public interface of the DAO), and how these needs can be satisfied with a specific DBMS, database schema, etc. (the implementation of the DAO).

INNER and OUTER join

INNER join return results that two tables have exact matches. (“where” use inner join)

An outer join does not require each record in the two joined tables to have a matching record. The joined table retains each record—even if no other matching record exists. including left outer join, right outer join, and full outer join, and the “outer” can be omitted.

check a column of table A but does not exist in table B

        ON A.id_string = B.id_string
    B.id_string IS NULL 
  AND A.id_string IS NOT NULL # can be ignored if id_string is forced to be required

difference between index and partition

Partitioning: -> physical partition of the table based on the characteristics which you have specified and stored on the different physical tables.
Fast for deleting  and loading tables. When using partition, rails treats as one big table logically, so no problem for one table related to one model.

Indexing->In the indexing there is no separate database tables.Its a logical.Only one index file (a B-tree) is created based on the characteristics which you mentioned.