Monday, May 27, 2019

XML- Extensible markup language

What is XML?

XML stands for eXtensible Markup Language
XML is a markup language much like HTML
XML was designed to store and transport data
XML was designed to be self-descriptive
XML is a W3C Recommendation

XML Does Not DO Anything

Maybe it is a little hard to understand, but XML does not DO anything.

This note is a note to Tove from Jani, stored as XML:

<note>
  <to>Tove</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>Don't forget me this weekend!</body>
</note>

The Difference Between XML and HTML

XML and HTML were designed with different goals:

XML was designed to carry data - with focus on what data is
HTML was designed to display data - with a focus on how data looks
XML tags are not predefined like HTML tags are.

XML

Saturday, May 25, 2019

Why Study JavaScript?

JavaScript is one of the 3 languages all web developers must learn:

1. HTML to define the content of web pages

2. CSS to specify the layout of web pages

3. JavaScript to program the behavior of web pages

Web pages are not the only place where JavaScript is used. Many desktop and server programs use JavaScript. Node.js is the best known. Some databases, like MongoDB and CouchDB, also use JavaScript as their programming language.

PL-SQL Concepts

PL-SQL Concepts Presentations.

PL SQL is procedural language or structured language.

The main feature of SQL (non-procedural) is also a drawback of SQL: one cannot use control statements (decision-making or iterative control) if only SQL is to be used.

PL/SQL is basically a procedural language, which provides the functionality of decision making, iteration and many more features like other procedural programming languages.

A PL/SQL program unit is one of the following: PL/SQL anonymous block, procedure, function, package specification, package body, trigger, type specification, type body, library. Program units are the PL/SQL source code that is compiled, developed and ultimately executed on the database.

Normalization in Database

Normalization

Normalization: Process to reduce redundancy.

Normalizing a Database:

Normalization is a process of reducing redundancies of data in a database. Normalization is a technique that is used when designing and redesigning a database.

Normalization is a process or set of guidelines used to optimally design a database to reduce redundant data.

The actual guidelines of normalization, called normal forms, will be discussed later in this hour.

It was a difficult decision to decide whether to cover normalization in this book because of the complexity involved in understanding the rules of the normal forms this early on in your SQL journey.

However, normalization is an important process that, if understood, will increase your understanding of SQL.

We have attempted to simplify the process of normalization as much as possible in this hour.

At this point, don't be overly concerned with all the specifics of normalization; it is most important to understand the basic concepts.

Transaction in Database and ACID properties

Database Transactions

In this presentation transactions in the database is explained.

In computer science, ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties of database transactions intended to guarantee validity even in the event of errors, power failures, etc. In the context of databases, a sequence of database operations that satisfies the ACID properties (and these can be perceived as a single logical operation on the data) is called a transaction. For example, a transfer of funds from one bank account to another, even involving multiple changes such as debiting one account and crediting another, is a single transaction.

SQL

SQL- Structured Query Language Presentations

SQL Quick Reference

SQL Statement	Syntax
AND / OR	SELECT column_name(s) FROM table_name WHERE condition AND\|OR condition
ALTER TABLE	ALTER TABLE table_name ADD column_name datatype or ALTER TABLE table_name DROP COLUMN column_name
AS (alias)	SELECT column_name AS column_alias FROM table_name or SELECT column_name FROM table_name AS table_alias
BETWEEN	SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2
CREATE DATABASE	CREATE DATABASE database_name
CREATE TABLE	CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name3 data_type, ... )
CREATE INDEX	CREATE INDEX index_name ON table_name (column_name) or CREATE UNIQUE INDEX index_name ON table_name (column_name)
CREATE VIEW	CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition
DELETE	DELETE FROM table_name WHERE some_column=some_value or DELETE FROM table_name (Note: Deletes the entire table!!) DELETE * FROM table_name (Note: Deletes the entire table!!)
DROP DATABASE	DROP DATABASE database_name
DROP INDEX	DROP INDEX table_name.index_name (SQL Server) DROP INDEX index_name ON table_name (MS Access) DROP INDEX index_name (DB2/Oracle) ALTER TABLE table_name DROP INDEX index_name (MySQL)
DROP TABLE	DROP TABLE table_name
EXISTS	IF EXISTS (SELECT * FROM table_name WHERE id = ?) BEGIN --do what needs to be done if exists END ELSE BEGIN --do what needs to be done if not END
GROUP BY	SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name
HAVING	SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value
IN	SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,..)
INSERT INTO	INSERT INTO table_name VALUES (value1, value2, value3,....) or INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,....)
INNER JOIN	SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LEFT JOIN	SELECT column_name(s) FROM table_name1 LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
RIGHT JOIN	SELECT column_name(s) FROM table_name1 RIGHT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
FULL JOIN	SELECT column_name(s) FROM table_name1 FULL JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LIKE	SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern
ORDER BY	SELECT column_name(s) FROM table_name ORDER BY column_name [ASC\|DESC]
SELECT	SELECT column_name(s) FROM table_name
SELECT *	SELECT * FROM table_name
SELECT DISTINCT	SELECT DISTINCT column_name(s) FROM table_name
SELECT INTO	SELECT * INTO new_table_name [IN externaldatabase] FROM old_table_name or SELECT column_name(s) INTO new_table_name [IN externaldatabase] FROM old_table_name
SELECT TOP	SELECT TOP number\|percent column_name(s) FROM table_name
TRUNCATE TABLE	TRUNCATE TABLE table_name
UNION	SELECT column_name(s) FROM table_name1 UNION SELECT column_name(s) FROM table_name2
UNION ALL	SELECT column_name(s) FROM table_name1 UNION ALL SELECT column_name(s) FROM table_name2
UPDATE	UPDATE table_name SET column1=value, column2=value,... WHERE some_column=some_value
WHERE	SELECT column_name(s) FROM table_name WHERE column_name operator value

Database Codd Rules

Codd Rules Presentation

DBMS | Relational Model Introduction and Codd Rules

Terminology

Relational Model: Relational model represents data in the form of relations or tables.

Relational Schema: Schema represents the structure of a relation. e.g.; Relational Schema of STUDENT relation can be represented as:
STUDENT (STUD_NO, STUD_NAME, STUD_PHONE, STUD_STATE, STUD_COUNTRY, STUD_AGE)

Relational Instance: The set of values present in relation to a particular instance of time is known as relational instance as shown in Table 1 and Table 2.

Attribute: Each relation is defined in terms of some properties, each of which is known as attribute. For Example, STUD_NO, STUD_NAME, etc. are attributes of relation STUDENT.

The domain of an attribute: The possible values an attribute can take in a relation is called its domain. For Example, the domain of STUD_AGE can be from 18 to 40.
Tuple: Each row of a relation is known as a tuple. e.g.; STUDENT relation given below has 4 tuples.

NULL values: Values of some attribute for some tuples may be unknown, missing or undefined which are represented by NULL. Two NULL values in a relation are considered different from each other.
Table 1 and Table 2 represent the relational model having two relations STUDENT and STUDENT_COURSE.

Codd Rules

Codd rules were proposed by E.F. Codd which should be satisfied by relational model.

Foundation Rule: For any system that is advertised as, or claimed to be, a relational data base management system, that system must be able to manage data bases entirely through its relational capabilities.
Information Rule: Data stored in Relational model must be a value of some cell of a table.
Guaranteed Access Rule: Every data element must be accessible by table name, its primary key and name of attribute whose value is to be determined.
Systematic Treatment of NULL values: NULL value in database must only correspond to missing, unknown or not applicable values.
Active Online Catalog: Structure of database must be stored in an online catalog which can be queried by authorized users.
Comprehensive Data Sub-language Rule: A database should be accessible by a language supported for definition, manipulation and transaction management operation.
View Updating Rule: Different views created for various purposes should be automatically updatable by the system.
High level insert, update and delete rule: Relational Model should support insert, delete, update etc. operations at each level of relations. Also, set operations like Union, Intersection and minus should be supported.
Physical data independence: Any modification in the physical location of a table should not enforce modification at application level.
Logical data independence: Any modification in logical or conceptual schema of a table should not enforce modification at application level. For example, merging of two tables into one should not affect application accessing it which is difficult to achieve.
Integrity Independence: Integrity constraints modified at database level should not enforce modification at application level.
Distribution Independence: Distribution of data over various locations should not be visible to end-users.
Non-Subversion Rule: Low level access to data should not be able to bypass integrity rule to change data.

Given the basic ER and relational models, which of the following is INCORRECT?

A. An attribute of an entity can have more than one value
B. An attribute of an entity can be composite
C. In a row of a relational table, an attribute can have more than one value
D. In a row of a relational table, an attribute can have exactly one value or a NULL value

Answer: In relation model, an attribute can’t have more than one value. So, option C is the answer.

Software Development Tools

Software Development Tools Presentation

From the moment you begin developing software, whether as a freelancer for a startup or working in a big company, having the right software development tools is essential. These tools cover a wide range of needs, from helping you organize your work to uploading and transferring files and much more.

Agile Methodology and Software Testing Techniques

Software Development Life Cycle

SDLC by Dinesh Kumar

Agile Methodology and Software Testing Techniques in One page

SDLC Agile Methodology and ... by Dinesh Kumar

SDLC- Software Development Life Cycle

Software Development Life Cycle Explained in this Presentation.

Software Development Life Cycle (SDLC) is a process used by the software industry to design, develop and test high quality softwares. The SDLC aims to produce a high-quality software that meets or exceeds customer expectations, reaches completion within times and cost estimates.

SDLC is the acronym of Software Development Life Cycle.
It is also called as Software Development Process.
SDLC is a framework defining tasks performed at each step in the software development process.
ISO/IEC 12207 is an international standard for software life-cycle processes. It aims to be the standard that defines all the tasks required for developing and maintaining software.

Coding Standards

Coding Standards Presentation

They are a series of procedures that can be defined for a particular programming language specifying a programming style, the methods, & different procedures. These procedures can be for various aspects of the program written in that language. They can be considered as essential attributes of software development.

A coding standard makes sure that all the developers working on the project are following certain specified guidelines. The code can be easily understood and a proper consistency is maintained.

Consistency has a positive impact on the quality of the program and one should maintain it while coding. Also, it should be taken care that the guidelines are homogeneously followed across different levels of the system and they do not contradict each other. The finished program code should look like that it has been written by a single developer, in a single session.

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