The SQL Guide to Pervasive PSQL. Rick F. van der Lans

Transcription

1 The SQL Guide to Pervasive PSQL Rick F. van der Lans

2 Copyright 2009 by R20/Consultancy All rights reserved; no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form of by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. Author: Rick F. van der Lans Title: The SQL Guide to Pervasive PSQL First Lulu edition 2009 Uploaded October 09 ISBN: Published by Lulu Edited by Diane Cools Book design by R20/Consultancy

3 Contents About the Author Foreword by Nancy Woodward Preface xiii xv xvii Part I to Pervasive PSQL Database, Database Server, and Database Language The Relational Model What Is SQL? The History of SQL From Monolithic via Client/Server to the Internet Standardization of SQL The History of Pervasive PSQL The Structure of This Book The Tennis Club Sample Database Description of the Tennis Club The Contents of the Tables Integrity Constraints Installing the Software Downloading Pervasive PSQL Installation of Pervasive PSQL Installing a Query Tool Downloading SQL Statements from the Website Ready? SQL in a Nutshell Creating Databases Creating New SQL Users Creating Tables Populating Tables with Data Querying Tables

4 vi The SQL Guide to Pervasive PSQL Updating and Deleting Rows Optimizing Query Processing with Indexes Views Users and Data Security Deleting Database Objects Grouping of SQL Statements The Catalog Tables Definitions of SQL Statements Part II Querying and Updating Data SELECT Statement: Common Elements Literals and their Data Types Expressions Assigning Names to Result Columns The Column Specification The System Variable The Case Expression The Scalar Expression Between Round Brackets The Scalar Function Casting of Expressions The Null Value as an Expression The Compound Scalar Expression The Aggregation Function and the Scalar Subquery The Row Expression The Table Expression SELECT Statements, Table Expressions, and Subqueries The Definition of the SELECT Statement Processing the Clauses in a Select Block Possible Forms of a Table Expression What is a SELECT Statement? What is a Subquery? SELECT Statement: the FROM Clause Table Specifications in the FROM Clause Again, the Column Specification Multiple Table Specifications in the FROM Clause Pseudonyms for Table Names Various Examples of Joins Mandatory Use of Pseudonyms Accessing Tables of Different Databases Explicit Joins in the FROM Clause Outer Joins Additional Conditions in the Join Condition The Cross Join The FROM Clause with Table Expressions

5 SELECT Statement: the WHERE Clause Conditions Using Comparison Operators Comparison Operators with Subqueries Comparison Operators with Correlated Subqueries Conditions Coupled with AND, OR, and NOT The IN Operator with Expression List The IN Operator with Subquery The BETWEEN Operator The LIKE Operator The IS NULL Operator The EXISTS Operator The ALL and ANY Operators Scope of Columns in Subqueries More Examples with Correlated Subqueries Conditions with Negation SELECT Statement: SELECT Clause and Aggregation Functions Selecting All Columns (*) Expressions in the SELECT Clause Removing Duplicate Rows with DISTINCT When Are Two Rows Equal? An to Aggregation Functions COUNT Function MAX and MIN Functions SUM and AVG Functions The Top Specification SELECT Statement: the GROUP BY Clause Grouping on One Column Grouping on Two or More Columns Grouping on Expressions Grouping of Null Values General Rules for the GROUP BY Clause Complex Examples with GROUP BY SELECT Statement: the HAVING Clause Examples of the HAVING Clause General Rule for the HAVING Clause SELECT Statement: the ORDER BY Clause Sorting on Column Names Sorting on Expressions Sorting with Sequence Numbers Sorting in Ascending and Descending Order Sorting of Null Values Contents vii

6 viii The SQL Guide to Pervasive PSQL Case Insensitive Sorting Combining Table Expressions Combining with UNION Rules for Using UNION Keeping Duplicate Rows with ALL Set Operators and the Null Value Updating Tables Inserting New Rows Populating a Table with Rows from Another Table Updating Values in Rows Deleting Rows from a Table Part III Creating Database Objects Databases Creating Databases Retrieving and Changing Data on Databases Security of Databases Dropping Databases Creating Tables Creating New Tables Data Types of Columns Creating Temporary Tables Naming Tables and Columns Default Value of a column Table Options Tables and the Catalog Integrity Constraints Primary Keys Alternate Keys Foreign Keys The Referencing Action Naming Integrity Constraints Non-modifiable Columns Deleting Integrity Constraints Integrity Constraints and the Catalog

7 Characters Sets and Collations The Character Sets of Pervasive PSQL Assigning a Collation to a Column Sorting with Collations The SET DEFAULTCOLLATE statement Changing and Dropping Tables Removing Entire Tables Renaming Tables Changing Table Characteristics Adding Columns Moving Columns Renaming Columns Changing Columns Dropping Columns Adding Integrity Constraints Dropping Integrity Constraints Decoupling Tables from Files Storage Structures and Indexes Rows, Tables, and Files How does an Index Work? Processing a SELECT statement: the Steps Creating Indexes Defining Partial Indexes Non-modifiable Indexes Decoupling Indexes from Files The Table Option LINKDUP Dropping Indexes Indexes and Primary Keys Indexes and Foreign Keys The Big PLAYERS_XXL Table Choosing columns for Indexes Hints, Indexes, and the Performance of Queries Indexes and the Catalog Views Creating Views The Column Names of Views Views and Privileges Deleting Views Views and the Catalog Restrictions on Changing the Contents of Views Processing View Statements Application Areas of Views Contents ix

8 x The SQL Guide to Pervasive PSQL Users and Data Security Adding and Removing users Changing the Names of Users Changing Passwords Granting Table and Column Privileges Granting Database Privileges Assigning Users to Groups Recording Privileges in the Catalog Revoking Privileges Security of and through Views Protecting the Catalog Tables Part IV Procedural Database Objects Stored Procedures An Example of a Stored Procedure The Parameters of a Stored Procedure The Body of a Stored Procedure Local Variables The SET Statement Flow Control Statements Calling Stored Procedures Querying Data with SELECT INTO Error Messages, SQLSTATE, and the SIGNAL Statement The BEGIN ATOMIC Statement A Set of Rows as Output Retrieving Data with a Cursor Updating and Deleting Data with a Cursor The Options of a Stored Procedure Stored Procedures and the Memory Cache Stored Procedures and the Catalog Removing Stored Procedures Security with Stored Procedures Advantages of Stored Procedures Stored Functions Examples of Stored Functions Removing Stored Functions Triggers An Example of a Trigger More Complex Examples Triggers and Integrity Constraints Removing Triggers Triggers and the Catalog

9 Transaction and Multi-user Usage What is a Transaction? Starting of Transactions Savepoints Stored Procedures and Transactions Problems with Multi-user Usage Locking Deadlocks The Isolation Level Waiting for a Lock Contents xi Appendices 565 A Syntax of SQL 565 B Scalar Functions 603 C System Stored Procedures 623 D Bibliography 633 Index 635