slides about : Introduction_to_SQL.pptx

1. Introduction to SQL
A Guide to Understanding and Using
SQL

2. Introduction to SQL
• SQL is a standard language for accessing and
manipulating databases.

3. What is SQL?
• SQL stands for Structured Query Language.
• SQL lets you access and manipulate databases.
• SQL became a standard of the ANSI in 1986,
and ISO in 1987.

4. What Can SQL Do?
• SQL can execute queries against a database.
• SQL can retrieve data from a database.
• SQL can insert, update, and delete records in a
database.
• SQL can create databases, tables, views, and
stored procedures.
• SQL can set permissions on tables,
procedures, and views.

5. SQL is a Standard - BUT...
• SQL is an ANSI/ISO standard, but there are
different versions.
• To comply with ANSI, major commands
(SELECT, UPDATE, DELETE, etc.) are supported
similarly.
• Most SQL database programs have proprietary
extensions in addition to the standard.

6. Using SQL in Your Website
• To build a website showing data from a
database, you need:
• - An RDBMS database program (e.g., MS
Access, SQL Server, MySQL).
• - A server-side scripting language (e.g., PHP,
ASP).
• - SQL to retrieve data.
• - HTML/CSS to style the page.

7. RDBMS
• RDBMS stands for Relational Database
Management System.
• RDBMS is the basis for SQL and modern
database systems (MySQL, SQL Server, etc.).
• Data in RDBMS is stored in database objects
called tables.
• A table is a collection of related data entries
consisting of columns and rows.

8. Tables, Fields, and Records
• A field is a column designed to maintain
specific information (e.g., CustomerID).
• A record (row) is each individual entry in a
table.
• Columns contain all information associated
with a specific field.

9. SQL Syntax
SQL Statements
• Most of the actions you need to perform on a
database are done with SQL statements.
• SQL statements consist of keywords that are
easy to understand.
• The following SQL statement returns all records
from a table named "Customers":
Example
• Select all records from the Customers table:
• SELECT * FROM Customers;

10. Keep in Mind That...
• SQL keywords are NOT case sensitive: select is the same as SELECT
• In this tutorial we will write all SQL keywords in upper-case.
Semicolon after SQL Statements?
• Some database systems require a semicolon at the end of each
SQL statement.
• Semicolon is the standard way to separate each SQL statement in
database systems that allow more than one SQL statement to be
executed in the same call to the server.
• In this tutorial, we will use semicolon at the end of each SQL
statement.

11. Some of The Most Important SQL Commands
•SELECT - extracts data from a database
•UPDATE - updates data in a database
•DELETE - deletes data from a database
•INSERT INTO - inserts new data into a
database
•CREATE DATABASE - creates a new database
•ALTER DATABASE - modifies a database
•CREATE TABLE - creates a new table
•ALTER TABLE - modifies a table
•DROP TABLE - deletes a table
•CREATE INDEX - creates an index (search key)
•DROP INDEX - deletes an index