SQL Overview

1
SQL Overview

• Structured Query Language

2
Description

• When Codd first described the theory of
  relational databases, he asserted that there
  should be a comprehensive language that would
  describe both the data and the meta data.
• SQL has developed into that language

3
SQL Features

• SQL does not come as a separate package
• It is always a part of a Data Base Management
  system
• SQL is a fourth generation language (meaning it
  is not procedural. You describe what you want to
  do not how to do it)

4
Standards

• SQL is an ANSI standard
• Most DBMS implement the 1992 standard, some are
  beginning to implement the 1999 standard
• In addition to the standard SQL most DBMSs add
  their own commands and features
• SQL Server has T-SQL
• Oracle has PSQL

5
Three Uses

• To define data (including setting indexes and
  user permissions)
• To query data
• To manipulate data

6
Data Definition

• You can define all the data structures in a
  relational database with SQL
• CREATE TABLE tblCustomer
• (
• CustomerID Integer Primary Key,
• CustomerLastName varchar(50),
• CustomerFirstName varchar(35)
• )

7
Data Query

• You can retrieve any data or combination of the
  data from the database with SQL queries
• SELECT CustomerLastName, CustomerFirstname,
  OrderID, OrderDate
• FROM tblCustomer c
• INNER JOIN tblOrder o
• ON c.CustomerIDo.CustomerID
• WHERE c.CustomerID5

8
Data Manipulation

• You can Insert, Update and Manipulate data with
  SQL
• UPDATE tblCustomer
• SET LastNameSmith
• WHERE CustomerID7