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
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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