Oracle SQL Tutorials – Chapter 1 (Part 1 of 3)

CHAPTER 1 – INTRODUCTION TO SQL

  • Explaining the capabilities of the SELECT statement
  • Writing simple SELECT statements
  • Select columns and aliases
  • Arithmetic operators
  • NULL value
  • Union operator
  • Usage of DISTINCT command

What is SQL ( Structured Query Language)

  • It is a language that being used to manage and querying the data in relational (RDBMS) databases.
  • It is not a programming language like C, C++ , Java. It is a sub-language that being used on databases like Oracle, SQL Server, Sybase, MySQL, DB2.
  • SQL is a language that allows the applications and users to acces the database and make changes.

Classification of the SQL Commands

  • SQL commands are classify under four parts as DDL, DML, DCL and TCL.
  • DDL : Data Definiton Language
  • DML : Data Manipulation Language
  • DCL : Data Control Language
  • TCL : Transaction Control Language

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Usage Areas of SQL

  • Modeling and managing the data & data models.
  • Selecting, adding, deleting and updating the data.
  • Creating, changing and deleting the database objects.
  • Controlling the access to the database and objects.
  • Providing the consistency and integrity of the database.

The Rules of Writing SQL

  • SQL statements are not case-sensitive.
  • SQL statements are formes in one or more lines.
  • Keywords can not be shortened or divided into lines ( SELECT, FROM, DISCTINCT etc.).
  • Keywords are usually placed in different lines.
  • Keywords are usually writing in upper-case.
  • Date and character data are alligned in left as default.
  • Numerical data are alligned in right as default.

 

 

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