tailieunhanh - SQL A Practical Introduction

SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks". Despite not adhering to the relational model as described by Codd, it became the most widely used database language. Although SQL is often described as, and to a great extent is, a declarative language (4GL), it also includes procedural elements. SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standards (ISO) in 1987. Since then, the standard has been. | CONTENTS 1 INTRODUCTION A Collection of Related Data Databases and Database Management Systems. The Database as a Collection of Tables Relational Databases and SQL. Tables Columns and Rows. The Primary Key. Communicating to the DBMS What You Want it to do Introduction to the SQL language. A Research Project Conducted by IBM The History of SQL. SQL Commands Build Upon Themselves Organization of This Book. Notational Conventions. 2 A ROUGH GUIDE TO SQL. Consider the Simple Address Book A Basic Relational Database. SQL Commands Fall into Different Categories Subdivisions of SQL. Enter SQL Statements at the Command Line Using interpretive SQL. Use the CREATE TABLE statement Creating Database Tables. Use the INSERT INTO Statement Adding Data to Tables. Use the SELECT Statement Extracting data from tables. Use the UPDATE and DELETE Statements Modifying data. Another Kind of Table Called a Virtual Table Views. Prevent Access to Sensitive Information Database security. 3 CREATING AND MAINTAINING TABLES. The ANSI Standard Makes Such a Distinction. The DDL and the ANSI ISO standard. Single and Multiple Database Architectures The structure of SQL databases. Creating a Database Table The CREATE TABLE command. Apply Restrictions to Groups of Columns Column and table modifiers. The NOT NULL modifier. The UNIQUE modifier. The INDEX modifier. The PRIMARY KEY modifier. The FOREIGN KEY modifier. The DEFAULT modifier. The CHECK modifier Indexes are Ordered for Extremely Fast Searches Indexes. Changing the Structure of a Table The ALTER TABLE Command. Remove Redundant Tables from the Database The DROP TABLE Command. 4 QUERYING SQL TABLES. The most basic query The Simple SELECT statement. Calculated columns. Selecting rows for output The WHERE clause. Comparison Test Operators . Range Test Operator BETWEEN. Set .