Preface

PL/SQL is Oracle's procedural extension to SQL, the standard database access language. A full-fledged programming language, PL/SQL offers modern software engineering features such as data encapsulation, overloading, exception handling, and information hiding. PL/SQL also offers seamless SQL access, tight integration with the Oracle server and tools, portability, and security.

This guide explains all the concepts behind PL/SQL and illustrates every facet of the language. Good programming style is stressed throughout and supported by numerous examples. Using this guide, you learn PL/SQL quickly and effectively, and you learn why PL/SQL is ideal for building enterprise-wide applications.

Major Topics

What's New in This Edition?

How This Guide Is Organized

Notational Conventions

Sample Database Tables

Audience

Anyone developing applications for Oracle will benefit from reading this guide. Written especially for programmers, this comprehensive treatment of PL/SQL will also be of value to systems analysts, project managers, and others interested in database applications. To use this guide effectively, you need a working knowledge of the following subjects:

• a procedural programming language such as Ada, C, or COBOL
• the SQL database language
• Oracle concepts and terminology

You will not find installation instructions or system-specific information in this guide. For that kind of information, see the Oracle installation or user's guide for your system.

What's New in This Edition?

Release 8.0 of PL/SQL offers an array of new features that help you build powerful database applications. For example, now you can benefit from

• an interface for calling routines written in other languages
• support for object-oriented programming based on object types
• the collection types TABLE and VARRAY, which allow you to declare nested tables and variable-size arrays
• the LOB (large object) datatypes BFILE, BLOB, CLOB, and NCLOB, which let you manipulate blocks of unstructured data up to four gigabytes in size
• extended National Language Support (NLS) including national character sets and the datatypes NCHAR and NVARCHAR2, which store NLS data

For more information, see Appendix A

Note: This guide applies to Oracle8 and the Oracle8 Enterprise Edition. They have the same basic features. However, several advanced features are available only with the Enterprise Edition, and some of these are optional. For example, to use object types, you must have the Enterprise Edition and the Objects Option. To find out which features are available to you, see Getting to Know Oracle8 and the Oracle8 Enterprise Edition.

How This Guide Is Organized

The PL/SQL User's Guide and Reference has 11 chapters and 6 appendices. Chapters 1 through 10 introduce you to PL/SQL and shows you how to use its many features. Chapter 11 serves as a reference to PL/SQL commands, syntax, and semantics. Appendices A through F provide a survey of new features, sample programs, supplementary technical information, and a list of reserved words.

Chapter 1: Overview

This chapter surveys the main features of PL/SQL and points out the advantages they offer. It also acquaints you with the basic concepts behind PL/SQL and the general appearance of PL/SQL programs.

Chapter 2: Fundamentals

This chapter focuses on the small-scale aspects of PL/SQL. It discusses lexical units, scalar datatypes, user-defined subtypes, data conversion, expressions, assignments, block structure, declarations, and scope.

Chapter 3: Control Structures

This chapter shows you how to structure the flow of control through a PL/SQL program. It describes conditional, iterative, and sequential control. You learn how to apply simple but powerful control structures such as IF-THEN-ELSE and WHILE-LOOP.

Chapter 4: Collections and Records

This chapter focuses on the composite datatypes TABLE, VARRAY, and RECORD. You learn how to reference and manipulate whole collections of data. You also learn how to treat related but dissimilar data as a logical unit.

Chapter 5: Interaction with Oracle

This chapter shows you how PL/SQL supports the SQL commands, functions, and operators that let you manipulate Oracle data. You also learn how to manage cursors, process transactions, and safeguard your database.

Chapter 6: Error Handling

This chapter provides an in-depth discussion of error reporting and recovery. You learn how to detect and handle errors using PL/SQL exceptions.

Chapter 7: Subprograms

This chapter shows you how to write and use subprograms. It discusses procedures, functions, forward declarations, actual versus formal parameters, positional and named notation, parameter modes, parameter default values, aliasing, overloading, and recursion.

Chapter 8: Packages

This chapter shows you how to bundle related PL/SQL types, items, and subprograms into a package. Once written, your general-purpose package is compiled, then stored in an Oracle database, where its contents can be shared by many applications.

Chapter 9: Object Types

This chapter introduces you to object-oriented programming based on object types, which provide abstract templates for real-world objects. You learn how to define object types and manipulate objects.

Chapter 10: External Procedures

This chapter presents a new PL/SQL interface for calling routines written in other languages. It shows you how dynamic link libraries (DLLs) already written and available in another language can be called directly from PL/SQL programs.

Chapter 11: Language Elements

This chapter uses syntax diagrams to show how commands, parameters, and other language elements are sequenced to form PL/SQL statements. Also, it provides usage notes and short examples to help you become fluent in PL/SQL quickly.

Appendix A: New Features

This appendix surveys the major new features in Release 8.0 of PL/SQL.

Appendix B: Sample Programs

This appendix provides several PL/SQL programs to guide you in writing your own. The sample programs illustrate important concepts and features.

Appendix C: CHAR versus VARCHAR2 Semantics

This appendix explains the subtle but important semantic differences between the CHAR and VARCHAR2 base types.

Appendix D: PL/SQL Wrapper

This appendix shows you how to run the PL/SQL Wrapper, a stand-alone utility that enables you to deliver PL/SQL applications without exposing your source code.

Appendix E: Name Resolution

Thus appendix explains how PL/SQL resolves references to names in potentially ambiguous procedural and SQL statements.

Appendix F: Reserved Words

This appendix lists those words reserved for use by PL/SQL.

Notational Conventions

This guide uses the following notation in code examples:

< >	Angle brackets enclose the name of a syntactic element.
--	A double hyphen begins a single-line comment, which extends to the end of a line.
/* */	A slash-asterisk and an asterisk-slash delimit a multi-line comment, which can span multiple lines.
...	An ellipsis shows that statements or clauses irrelevant to the discussion were left out.
lower case	Lower case denotes user-defined items such as variables, parameters, and exceptions.
UPPER CASE	Upper case denotes PL/SQL keywords.

Terms being defined for the first time, words being emphasized, error messages, and book titles are italicized.

The syntax of PL/SQL is described using a simple variant of Backus-Naur Form (BNF), which has the following symbols and lexical conventions:

[ ]	Brackets enclose optional items.
{ }	Braces enclose items only one of which is required.
|	A vertical bar separates alternatives within brackets or braces.
...	An ellipsis shows that the preceding syntactic element can be repeated.
lower case	Lower case denotes a syntactic element for which you must substitute a literal, identifier, or construct, whichever is appropriate.
UPPER CASE	Upper case denotes PL/SQL keywords, which must be spelled as shown but can be entered in lower or mixed case.
punctuation	Punctuation other than brackets, braces, vertical bars, and ellipses must be entered as shown.

Sample Database Tables

Most programming examples in this guide use two sample database tables named dept and emp. Their definitions follow:

CREATE TABLE dept (deptno NUMBER(2) NOT NULL,
                   dname  VARCHAR2(14),
                   loc    VARCHAR2(13))

CREATE TABLE emp (empno    NUMBER(4) NOT NULL,
                  ename    VARCHAR2(10),
                  job      VARCHAR2(9),
                  mgr      NUMBER(4),
                  hiredate DATE,
                  sal      NUMBER(7,2),
                  comm     NUMBER(7,2),
                  deptno   NUMBER(2))

Sample Data

Respectively, the dept and emp tables contain the following rows of data:

DEPTNO  DNAME      LOC
------- ---------- ---------
10      ACCOUNTING NEW YORK
20      RESEARCH   DALLAS
30      SALES      CHICAGO
40      OPERATIONS BOSTON

EMPNO ENAME   JOB          MGR  HIREDATE    SAL   COMM  DEPTNO
----- ------- --------- ------ --------- ------ ------ -------
 7369 SMITH   CLERK       7902 17-DEC-80    800             20
 7499 ALLEN   SALESMAN    7698 20-FEB-81   1600    300      30
 7521 WARD    SALESMAN    7698 22-FEB-81   1250    500      30
 7566 JONES   MANAGER     7839 02-APR-81   2975             20
 7654 MARTIN  SALESMAN    7698 28-SEP-81   1250   1400      30
 7698 BLAKE   MANAGER     7839 01-MAY-81   2850             30
 7782 CLARK   MANAGER     7839 09-JUN-81   2450             10
 7788 SCOTT   ANALYST     7566 19-APR-87   3000             20
 7839 KING    PRESIDENT        17-NOV-81   5000             10
 7844 TURNER  SALESMAN    7698 08-SEP-81   1500             30
 7876 ADAMS   CLERK       7788 23-MAY-87   1100             20
 7900 JAMES   CLERK       7698 03-DEC-81    950             30
 7902 FORD    ANALYST     7566 03-DEC-81   3000             20
 7934 MILLER  CLERK       7782 23-JAN-82   1300             10

Your Comments Are Welcome

We appreciate your comments and suggestions. In fact, your opinions are the most important feedback we receive. We encourage you to use the Reader's Comment Form at the front of this guide. You can also send comments to us by

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