Introduction to SQL

Table of Contents

1 SQL Data Definition and Data Types
    1.1 Schema and Catalog
    1.2 CREATE TABLE Command
    1.3 Data Types
2 Specifying Constraints in SQL
    2.1 Attribute Constraints
    2.2 Key and Referential Integrity Constraints
    2.3 Naming Constraints
    2.4 Using CHECK
3 Basic Retrieval Queries in SQL
    3.1 SELECT FROM WHERE
    3.2 Qualifying Attribute Names
    3.3 Querying without WHERE Clause and Using the Asterisk
    3.4 Duplicate Tuples and Distinct Tuples
    3.5 LIKE Operator, Arithmetic Operators, BETWEEN...AND Operator
    3.5 Ordering-Query-Results
4 INSERT, DELETE, and UPDATE Statements
    4.1 INSERT
    4.2 DELETE
    4.3 UPDATE

---

The SQL language is a standard for relational databases:

• since database systems share a standard language, migrating a database application to another relational database is a quick and inexpensive process
• database application programs can access data stored in multiple relational DBMSs using the same database language

The practical SQL vs the relational algebra

• the SQL language is a high level declarative language for the relational model: with a query in the SQL language, the user must only indicate how the result is to be and the DBMS decides how to execute the query
• the relational algebra is a formal language for the relational model: with a query in the relational algebra, the user must specify a sequence of low-level operations. Relational algebra operations are not suitable for most DBMS users

The SQL name stands for Structured Query Language

• the SQL language is a standard by the American National Standards Institute (ANSI) and the International Standards Organization (ISO)
• on the wikipedia page about SQL, you can find out the history of the versions of the SQL standard

The Company Database Application

Table of Contents

    1 The Database Design Process
    2 STEP #1: Collection and analysis of requirements
    3 STEP #2: Conceptual design of the database with the ER model
    4 STEP #3: Logical design
    5 STEP #4: Physical design

1 The Database Design Process

A diagram to illustrate the phases of database design process

Introduction To Database

Table of Contents

Databases and Database Users
    1 Introduction
    2 Database Characteristics
    3 Database Actors
    4 Data Models, Schemas, and Instances
Database System Concepts
    5 Three-Schema Architecture and Data Independence
    6 Database Languages

Databases and Database Users

Many daily activities involve the use of applications that interact with a database, for example making a bank operation or an hotel reservations, borrowing a book, purchasing tickets or anything else online.

A database application manages information that is to be stored in a database:

• traditional applications use databases to store textual or numeric data
• social-media web sites use big data storage systems or NOSQL systems to store text data and non conventional data such as images and video data