Data Structure & Algorithms

Data Structures are the programmatic way of storing data so that data can be used efficiently. Almost every enterprise application uses various types of data structures in one or other way.

Memcached Tutorial

Memcached is an open source, high-performance, distributed memory object caching system.

Memcached is an open source, high-performance, distributed memory caching system intended to speed up dynamic web applications by reducing the database load.

It is a key-value dictionary of strings, objects, etc, stored in the memory, resulting from database calls, API calls, or page rendering.

Memcached was developed by Brad Fitzpatrick for LiveJournal in 2003.

It is open source.

Memcached server is a big hash table.
(Hash Table is a data structure which store data in associative manner. In hash table, data is stored in array format where each data values has its own unique index value.)

It significantly reduces the database load.

It is perfectly efficient for websites with high database load.

It is a client-server application over TCP and/or UDP.

Memcached is not −
A persistent data store
(Persistent storage is any data storage device that retains data after power to that device is shut off. It is also sometimes referred to as non-volatile storage. )

A database

Application-specific

A large object cache

Fault-tolerant or

Highly available

Add Method in Jquery

<script>

$(document).ready(function(){

 

 $("#pop_report_form").validate({

 rules: {

hdn_select_any: {

 selectOne:true

}

},

 });

$.validator.addMethod("selectOne", function(value, element) {

var set_name = $('#set_name').val();

var player_name = $('#player_name').val();

if((player_name != '' && player_name != 'Player Name') || (set_name != '' && set_name != 'Set Name'))

{

return true; 

}

else

{

 return false;

}

}, function() {return 'Please Select Set or Player '});

});

</script>

Authenticate

    if (!isset($_SERVER['PHP_AUTH_USER'])) {
            header("WWW-Authenticate: Basic realm=\"Private Area\"");
            header("HTTP/1.0 401 Unauthorized");
            print "Please enter your username and password!\n";
            exit;
        } else {
            if (($_SERVER['PHP_AUTH_USER'] == 'modaym') && ($_SERVER['PHP_AUTH_PW'] == 'modaym123#')) {
               
            } else {
                header("WWW-Authenticate: Basic realm=\"Private Area\"");
                header("HTTP/1.0 401 Unauthorized");
                print "Please enter your username and password!\n";
                exit;
            }
        }

What's Stored Procedure

Stored Procedure is a Set precompiled Sql statements that used to Perform A special Task.
Stored Procedures are a batch of SQL statements that can be executed in a couple of ways.

A stored procedure, which calls itself, is recursive stored procedure. Almost RDMBS supports recursive stored procedure but MySQL does not support it well. Check your version of MySQL before using recursive stored procedure

• SP have repeatedly using data. It helps to reuse the code.
• SP is reduces the complexity of code in code behind.
• SP increase the security to application, it protect from Sql injection and hacking.
• Code maintenance and changes are done very easily. Instead of changing the code in code behind if changes required.

What is Locking in MySQL

Locking can be crucial to avoid two users modifying data at the same time. You may think that's unlikely, but depending on the application, there is a significant risk if the same data is frequently changed by different users.
Imagine the following situation without using locks: John opens his screen (he doesn't know he's using a database, he is only an end user who is looking at a pretty screen), modifies some data, and then hits "Save". Let's say John open the screen at 9:30 and then saves the data at 9:32.
However, Mary opened exactly the same screen and the same record at 9:29. She saw at that time the same data that John did at 9:30. Then, she updates the record, and hits "Save" at 9:31.
What data was saved? John's or Mary's?

MySQL Storage engines

A storage engine is a software which a DataBase management System uses to create, read, update and delete data from a database. - See more at: http://www.w3resource.com/mysql/mysql-storage-engines.php#sthash.Dyo7hV6k.dpuf

A storage engine is a software module that a DBMS uses to create, read, update and  delete (CRUD) data from a database. There are two types of storage engines in MySQL. Transactional and non-transactional.

The default storage engine for MySQL prior to version 5.5 was MyISAM. For MySQL 5.5 and later, the default storage engine is InnoDB. Choosing the right storage engine is an important strategic decision, which will impact future development. In this tutorial, we will be using MyISAM, InnoDB, Memory and CSV storage engines. If you are new to MySQL and your are studying the MySQL database management system, then this is not much of a concern. If you are planning a production database, then things become more complicated.

 

List of storage engines

MySQL supported storage engines:

• MyISAM
• InnoDB
• Memory
• CSV
• Merge
• Archive
• Federated
• Blackhole
• Example

MyISAM is the original storage engine. It is a fast storage engine. It does not support transactions. MyISAM provides table-level locking. It is used most in Web, data warehousing.

InnoDB is the most widely used storage engine with transaction support. It is an ACID compliant storage engine. It supports row-level locking, crash recovery and multi-version concurrency control. It is the only engine which provides foreign key referential integrity constraint.

Memory storage engine creates tables in memory. It is the fastest engine. It provides table-level locking. It does not support transactions. Memory storage engine is ideal for creating temporary tables or quick lookups. The data is lost when the database is restarted.

CSV stores data in csv files. It provides great flexibility, because data in this format is easily integrated into other applications.

Merge operates on underlying MyISAM tables. Merge tables help manage large volumes of data more easily. It logically groups a series of identical MyISAM tables, and references them as one object. Good for data warehousing environments.

Archive storage engine is optimized for high speed inserting. It compresses data as it is inserted. It does not support transactions. It is ideal for storing, retrieving large amounts of seldom referenced historical, archived data.

The Blackhole storage engine accepts but does not store data. Retrievals always return an empty set. The functionality can be used in distributed database design where data is automatically replicated, but not stored locally. This storage engine can be used to perform performance tests or other testing.

Federated storage engine offers the ability to separate MySQL servers to create one logical database from many physical servers. Queries on the local server are automatically executed on the remote (federated) tables. No data is stored on the local tables. It is good for distributed environments.

Choosing the right engine

No storage engine is ideal for all circumstances. Some perform best under certain conditions and perform worse in other situations. There are tradeoffs than must be considered. A more secure solution takes more resources. It might be slower, take more CPU time and disk space. MySQL is very flexible in the fact that it provides several different storage engines. Some of them, like the Archive engine, are created to be used in specific situations. Ironically this also brings a question, which storage engine to use? Which may not be easily answered.
In some cases, the answer is clear. Whenever we are dealing with some payment systems, we are obliged to use the most secure solution. We cannot afford to loose such sensitive data. InnoDB is the way to go. If we want full-text search, than we must choose MyISAM. Only InnoDB supports foreign key referential integrity constraint and if we plan to use this constraint, then the choice is clear. In many situations we must have enough experience to choose the right engine. And if we lack the experience, than the best way is to ask some seasoned developer. One of the best ways is to ask on specific internet forums. stackoverflow.com is a great one. The question is further complicated by the fact, that we can choose different storage engines for different tables.

Specifying and altering storage engines

The storage engine is specified at the time of the table creation.

mysql> CREATE TABLE Cars(Id INTEGER PRIMARY KEY, Name VARCHAR(50), 
    -> Cost INTEGER) ENGINE='MyISAM';

The ENGINE keyword specifies the storage engine used for this particular table.
If we do not specify the storage engine explicitly, then the default storage engine is used. Prior to MySQL 5.5 the default storage engine was MyISAM. For MySQL 5.5 and later, the default storage engine is InnoDB.

mysql> SHOW VARIABLES LIKE 'storage_engine';
+----------------+--------+
| Variable_name  | Value  |
+----------------+--------+
| storage_engine | InnoDB |
+----------------+--------+
1 row in set (0.00 sec)

The default storage engine can be found in the storage_engine variable.
It is possible to migrate to a different storage engine. Note that migrating a large table might take a long time. Also we might run into some problems when migrating tables. Some features might not be supported in both tables.

mysql> SELECT ENGINE FROM information_schema.TABLES
    -> WHERE TABLE_SCHEMA='mydb'
    -> AND TABLE_NAME='Cars';
+--------+
| ENGINE |
+--------+
| InnoDB |
+--------+
1 row in set (0.00 sec)

This SQL statement finds out the storage engine used for a Cars table in mydb database. We could also use SELECT CREATE TABLE Cars SQL statement. The information_schema is a table which stores technical information about our tables.

mysql> ALTER TABLE Cars ENGINE='MyISAM';

This SQL statement changes the storage engine to MyISAM.

mysql> SELECT ENGINE FROM information_schema.TABLES
    -> WHERE TABLE_SCHEMA='mydb'
    -> AND TABLE_NAME='Cars';
+--------+
| ENGINE |
+--------+
| MyISAM |
+--------+
1 row in set (0.00 sec)

Now the storage engine is MyISAM.