Database Design Best Practices - part 1

Never create multiple tables for storing similar information.

Suppose, you are going to make an inventory software for a shop where you will need to store purchase, sales and transfer information. You have two choices.

One is to create multiple tables for "purchase", "sales" and "transfer" information.

Second is to make a common table for every transaction of products for all of the given type of transactions.

Second is better.

Example:

Bad Practice
table: purchase (pur_id, date, order_by)
table: sales (sales_id, date, order_by)
table: transfer (tr_id, date, order_by)

Best Practice
table: orders (id, date, order_by, order_type)

(Here, bracketed elements are the names of attributes or fields of the table.)

"Live Security Platinum" Malware Problem and Step by Step Solution

Recently, I have faced some problem regarding a virus named "Live Security Platinum". It comes to my pc automatically while browsing unknown websites. It appears as following image at desktop:

If you get similar message in your pc, never click on the bubble, not even (x) or settings icon. Wherever you click, it will start a window where you will see a list of infected files of you computer and Live Security Platinum will stop all other executable files and make great damages on them.

If you have done the mistake and clicked on it, just don't wait, restart you computer as soon as possible. After restart, go to Start>All Programs>Live Security Platinum(folder, don't click at it's executable file) then click right button of your mouse keeping the cursor on Live Security Platinum's executable file and select "Open File Location". Delete all files at that location and then uninstall the software from "Program Files>Programs & Features".

Simulation of Link State Routing Algorithm Using PHP

Link State is one of the main routing protocols. Purpose of any routing protocols is to dynamically communicate information about all network paths used to reach a destination and to select from those paths, the best path to reach a destination network. Link state algorithm selects routing paths with lowest costs that are calculated using a distance metric iteratively checking them from each node. 

 

A link-state routing protocol is one of the two main classes of routing protocols used in packet switching networks for computer communications (the other is the distance-vector routing protocol). Examples of link-state routing protocols include OSPF and IS-IS.

The link-state protocol is performed by every switching node in the network (i.e. nodes that are prepared to forward packets; in the Internet, these are called routers). The basic concept of link-state routing is that every node constructs a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical path from it to every possible destination in the network. The collection of best paths will then form the node's routing table.

This contrasts with distance-vector routing protocols, which work by having each node share its routing table with its neighbors. In a link-state protocol the only information passed between nodes is connectivity related.

Link state algorithms are sometimes characterized informally as each router 'telling the world about its neighbors'. 

Pseudo-code of Link State Algorithm is presented below:

1. Initialization
2. N’ = u
3. For all nodes v
4.     If v is a neighbor of u
5.         Then D(v) = c(u, v)
6.     Else
7.         D(v) = µ
8. Loop
9. Find w not in N’ such that D(w) is minimum
10. Add w to N’
11. Update D(v) for each neighbor v of w and not in N’
12.     D(v) = min( D(v), D(w)+c(w,r) )
13. /*
14. Least path cost to w plus cost from w to v */
15.  Until N’=N

Link State algorithm is implemented using PHP with Html and Javascript interface. Below I am presenting the implementation.

Download Script: http://dl.dropbox.com/u/47625598/linkstate/index.php