What is SQL, and why is it useful?

SQL 

        SQL, the Structured Query Language, is a standardized relational database access language. It is

useful because it allows a user to query, manipulate, define, and control data in an RDBMS. SQL is
sanctioned by ANSI, which determines standards on all aspects of SQL, including data types. However,
most relational database products, including Oracle, have their own extensions to the ANSI standard,
providing additional functionality within their respective products by further extending the use of SQL.
By learning SQL, you will be able to use the language on other non-Oracle databases with some minor
syntax adjustments.
SQL (pronounced “sequel”) is an acronym for Structured Query Language, a standardized
language used to access and manipulate data. The history of SQL corresponds closely with the
development of a relational databases concept published in a paper by Dr. E. F. Codd at IBM in 1970

Why Learn SQL?

SQL is accepted as the universal standard database access language.
SQL is used by most commercial database applications.
Although the language has evolved over the years with a large array of syntax enhancements and additions, most of the basic functionality has remained essentially unchanged. SQL knowledge will continue to be a fundamental skill because there is currently no mature and viable alternative language that accomplishes the same functionality. Learning Oracle’s specific SQL implementation allows you great insight into the feature-rich functionality of one of the largest and most successful database vendors.

An Introduction to Databases

What is a database? A database is an organized collection of data. A database

management system (DBMS) is software that allows the creation, retrieval, and manipulation of data. You use such systems to maintain patient data in a hospital,

bank accounts in a bank, or inventory in a warehouse.

A relational database management system (RDBMS) provides this functionality within the context of the relational database theory and the rules defined for Relational databases by Codd. These rules, called “Codd’s Twelve Rules,”

What Is Data?

Data is all around you; you make use of it every day. Your hair may be brown, your flight leaves from gate K10, you try to get up in the morning at 6:30 A.M. Storing data in related groups and making the connections among them are what databases are all about

How Is Data Organized?

Relational databases offer data independence, meaning a user does not need to know on which hard drive and file a particular piece of information is stored. The RDBMS provides users with data consistency and data integrity.

A relational database stores data in tables, essentially a two-dimensional matrix consisting of columns and rows. Let’s start with a discussion of the terminology used in relational databases. For example, if an employee works in the finance department, and we know that he can work for only one

department, then there should not be duplicate department records or contradicting data in the database. As you work through this lab, you will discover many of these useful and essential features.

A relational database stores data in tables, essentially a two-dimensional matrix consisting of columns and rows. Let’s start with a discussion of the terminology used in relational databases.

Tables

A table typically contains data about a single subject. Each table has a unique name that signifies the contents of the data. A database usually consists of many tables. For example, you may store data about books you read in a table called BOOK and store details about authors in the AUTHOR table.

Columns

Columns in a table organize the data further, and a table consists of at least one column. Each column represents a single, low-level detail about a particular set of data. The name of the column is unique within a table and identifies the data you find in the column. For example, the BOOK table may have a column for the title, publisher, date the book was published, and so on. The order of the columns is unimportant because SQL allows you to display data in any order you choose.

Rows

Each row usually represents one unique set of data within a table.

Primary Key

When working with tables, you must understand how to uniquely identify data within a table. This is the purpose of the primary key