Oracle® Database
Application Developer's Guide - Fundamentals
10g Release 1 (10.1)
Part No. B10795-01
December 2003
Oracle Database Application Developer's Guide - Fundamentals, 10g Release 1 (10.1)
Part No. B10795-01
Copyright © 1996, 2003 Oracle Corporation. All rights reserved.
Primary Authors: Drew Adams, Eric Paapanen
Contributing Authors: M. Cowan, R. Moran, J. Russell, R. Strohm
Contributors: D. Alpern, G. Arora, C. Barclay, D. Bronnikov, T. Chang, M. Davidson, G. Doherty, D.
Elson, A. Ganesh, M. Hartstein, J. Huang, N. Jain, R. Jenkins Jr., S. Kotsovolos, S. Kumar, C. Lei, D.
Lorentz, R. Murthy, R. Pang, B. Sinha, S. Vemuri, W. Wang, D. Wong, A. Yalamanchi, Q. Yu
Graphic Designer: V. Moore
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Tight Integration with Oracle Database 1-5
Better Performance 1-5
iv
Higher Productivity 1-6
Scalability 1-6
Maintainability 1-6
PL/SQL Support for Object-Oriented Programming 1-6
Object Types 1-6
Collections 1-7
Portability 1-7
Security 1-7
Built-In Packages for Application Development 1-7
Built-In Packages for Server Management 1-8
Built-In Packages for Distributed Database Access 1-8
Overview of Java Support Built Into the Database 1-8
Overview of Oracle JVM 1-8
Overview of Oracle Extensions to JDBC 1-9
JDBC Thin Driver 1-10
JDBC OCI Driver 1-10
JDBC Server-Side Internal Driver 1-11
Oracle Database Extensions to JDBC Standards 1-11
Sample JDBC 2.0 Program 1-12
Sample Pre-2.0 JDBC Program 1-12
JDBC in SQLJ Applications 1-13
Overview of Oracle SQLJ 1-13
Benefits of SQLJ 1-15
Comparing SQLJ with JDBC 1-15
SQLJ Stored Procedures in the Server 1-16
Overview of Oracle JPublisher 1-17
Overview of Java Stored Procedures 1-17

OraParamArray 1-36
OraSQLStmt 1-36
OraAQ 1-36
OraAQMsg 1-37
OraAQAgent 1-37
Support for Oracle LOB and Object Datatypes 1-37
OraBLOB and OraCLOB 1-38
OraBFILE 1-38
Oracle Data Control 1-39
Oracle Objects for OLE C++ Class Library 1-39
Additional Sources of Information 1-39
Choosing a Programming Environment 1-40
Choosing Whether to Use OCI or a Precompiler 1-40
Using Built-In Packages and Libraries 1-41
vi
Java Compared to PL/SQL 1-41
PL/SQL Is Optimized for Database Access 1-42
PL/SQL Is Integrated with the Database 1-42
Both Java and PL/SQL Have Object-Oriented Features 1-42
Java Is Used for Open Distributed Applications 1-42
Part II Designing the Database
2 Selecting a Datatype
Summary of Oracle Built-In Datatypes 2-2
Representing Character Data 2-8
Column Lengths for Single-Byte and Multibyte Character Sets 2-9
Implicit Conversion Between CHAR/VARCHAR2 and NCHAR/NVARCHAR2 2-10
Comparison Semantics 2-10
Representing Numeric Data with Number and Floating-Point Datatypes 2-11
Floating-Point Number System Concepts 2-12
About Floating-Point Formats 2-12

Storing Dates in Character Datatypes 2-27
Viewing Date Settings 2-28
Altering Date Settings 2-29
Troubleshooting Y2K Problems in Applications 2-29
Representing Conditional Expressions as Data 2-32
Representing Geographic Coordinate Data 2-33
Representing Image, Audio, and Video Data 2-33
Representing Searchable Text Data 2-34
Representing Large Amounts of Data 2-34
Using RAW and LONG RAW Datatypes 2-35
Addressing Rows Directly with the ROWID Datatype 2-36
Extended ROWID Format 2-36
Different Forms of the ROWID 2-37
ROWID Pseudocolumn 2-37
Internal ROWID 2-37
External Character ROWID 2-37
External Binary ROWID 2-38
ROWID Migration and Compatibility Issues 2-38
Accessing Oracle Database Version 7 from an Oracle9i Client 2-39
Accessing an Oracle9i Database from a Client of Oracle Database Version 7 2-39
Import and Export 2-39
ANSI/ISO, DB2, and SQL/DS Datatypes 2-39
How Oracle Database Converts Datatypes 2-40
Datatype Conversion During Assignments 2-41
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Datatype Conversion During Expression Evaluation 2-43
Representing Dynamically Typed Data 2-44
Representing XML Data 2-47
3 Maintaining Data Integrity Through Constraints
Overview of Integrity Constraints 3-2

Restrictions on CHECK Constraints 3-16
Designing CHECK Constraints 3-16
Rules for Multiple CHECK Constraints 3-17
Choosing Between CHECK and NOT NULL Integrity Constraints 3-17
Examples of Defining Integrity Constraints 3-17
Example: Defining Integrity Constraints with the CREATE TABLE Command 3-18
Example: Defining Constraints with the ALTER TABLE Command 3-18
Privileges Required to Create Constraints 3-19
Naming Integrity Constraints 3-19
Enabling and Disabling Integrity Constraints 3-19
Why Disable Constraints? 3-20
About Exceptions to Integrity Constraints 3-20
Enabling Constraints 3-20
Creating Disabled Constraints 3-21
Enabling and Disabling Existing Integrity Constraints 3-21
Enabling Existing Constraints 3-21
Disabling Existing Constraints 3-22
Tip: Using the Data Dictionary to Find Constraints 3-22
Guidelines for Enabling and Disabling Key Integrity Constraints 3-23
Fixing Constraint Exceptions 3-23
Altering Integrity Constraints 3-23
Renaming Integrity Constraints 3-24
Dropping Integrity Constraints 3-25
Managing FOREIGN KEY Integrity Constraints 3-26
Datatypes and Names for Foreign Key Columns 3-26
Limit on Columns in Composite Foreign Keys 3-26
Foreign Key References Primary Key by Default 3-26
Privileges Required to Create FOREIGN KEY Integrity Constraints 3-27
Choosing How Foreign Keys Enforce Referential Integrity 3-27
Viewing Definitions of Integrity Constraints 3-28

Rolling Back Transactions 5-5
Defining Transaction Savepoints 5-6
An Example of COMMIT, SAVEPOINT, and ROLLBACK 5-6
Privileges Required for Transaction Management 5-7
Ensuring Repeatable Reads with Read-Only Transactions 5-7
Using Cursors within Applications 5-8
Declaring and Opening Cursors 5-9
Using a Cursor to Execute Statements Again 5-9
Closing Cursors 5-10
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Cancelling Cursors 5-10
Locking Data Explicitly 5-10
Choosing a Locking Strategy 5-11
When to Lock with ROW SHARE and ROW EXCLUSIVE Mode 5-12
When to Lock with SHARE Mode 5-12
When to Lock with SHARE ROW EXCLUSIVE Mode 5-14
When to Lock in EXCLUSIVE Mode 5-15
Privileges Required 5-15
Letting Oracle Database Control Table Locking 5-15
Explicitly Acquiring Row Locks 5-16
About User Locks 5-17
When to Use User Locks 5-18
Example of a User Lock 5-18
Viewing and Monitoring Locks 5-19
Using Serializable Transactions for Concurrency Control 5-19
How Serializable Transactions Interact 5-21
Setting the Isolation Level of a Transaction 5-23
The INITRANS Parameter 5-23
Referential Integrity and Serializable Transactions 5-23
Using SELECT FOR UPDATE 5-24

Sample Multiple-Row Query Using Native Dynamic SQL 6-10
Choosing Between Native Dynamic SQL and the DBMS_SQL Package 6-11
Advantages of Native Dynamic SQL 6-11
Native Dynamic SQL is Easy to Use 6-12
Native Dynamic SQL is Faster than DBMS_SQL 6-14
Performance Tip: Using Bind Variables 6-14
Native Dynamic SQL Supports User-Defined Types 6-15
Native Dynamic SQL Supports Fetching Into Records 6-15
Advantages of the DBMS_SQL Package 6-16
DBMS_SQL is Supported in Client-Side Programs 6-16
DBMS_SQL Supports DESCRIBE 6-16
DBMS_SQL Supports SQL Statements Larger than 32KB 6-16
DBMS_SQL Lets You Reuse SQL Statements 6-16
Examples of DBMS_SQL Package Code and Native Dynamic SQL Code 6-17
Querying Using Dynamic SQL: Example 6-17
Performing DML Using Dynamic SQL: Example 6-19
Performing DML with RETURNING Clause Using Dynamic SQL: Example 6-19
Using Dynamic SQL in Languages Other Than PL/SQL 6-20
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7 Using Procedures and Packages
Overview of PL/SQL Program Units 7-2
Anonymous Blocks 7-2
Stored Program Units (Procedures, Functions, and Packages) 7-4
Naming Procedures and Functions 7-5
Parameters for Procedures and Functions 7-5
Parameter Modes 7-6
Parameter Datatypes 7-7
%TYPE and %ROWTYPE Attributes
7-7
Tables and Records 7-8

When Does a Signature Change? 7-25
Modes 7-25
Default Parameter Values 7-26
Examples of Changing Procedure Signatures 7-26
Controlling Remote Dependencies 7-28
Dependency Resolution 7-29
Suggestions for Managing Dependencies 7-29
Cursor Variables 7-30
Declaring and Opening Cursor Variables 7-31
Examples of Cursor Variables 7-31
Fetching Data 7-31
Implementing Variant Records 7-32
Handling PL/SQL Compile-Time Errors 7-33
Handling Run-Time PL/SQL Errors 7-35
Declaring Exceptions and Exception Handling Routines 7-36
Unhandled Exceptions 7-38
Handling Errors in Distributed Queries 7-38
Handling Errors in Remote Procedures 7-38
Debugging Stored Procedures 7-40
Calling Stored Procedures 7-43
A Procedure or Trigger Calling Another Procedure 7-43
Interactively Calling Procedures From Oracle Database Tools 7-44
Calling Procedures within 3GL Applications 7-45
Name Resolution When Calling Procedures 7-45
Privileges Required to Execute a Procedure 7-45
Specifying Values for Procedure Arguments 7-46
Calling Remote Procedures 7-47
Remote Procedure Calls and Parameter Values 7-47
Referencing Remote Objects 7-48
Synonyms for Procedures and Packages 7-49

8 Calling External Procedures
Overview of Multi-Language Programs 8-2
What Is an External Procedure? 8-3
Overview of The Call Specification for External Procedures 8-4
Loading External Procedures 8-4
Loading Java Class Methods 8-5
xvi
Loading External C Procedures 8-5
Publishing External Procedures 8-10
The AS LANGUAGE Clause for Java Class Methods 8-12
The AS LANGUAGE Clause for External C Procedures 8-12
LIBRARY 8-12
NAME 8-12
LANGUAGE 8-12
CALLING STANDARD 8-12
WITH CONTEXT 8-13
PARAMETERS 8-13
AGENT IN 8-13
Publishing Java Class Methods 8-13
Publishing External C Procedures 8-14
Locations of Call Specifications 8-14
Example: Locating a Call Specification in a PL/SQL Package Body 8-15
Example: Locating a Call Specification in an Object Type Specification 8-16
Example: Locating a Call Specification in an Object Type Body 8-16
Passing Parameters to External C Procedures with Call Specifications 8-18
Specifying Datatypes 8-19
External Datatype Mappings 8-21
BY VALUE/REFERENCE for IN and IN OUT Parameter Modes 8-23
The PARAMETERS Clause 8-24
Overriding Default Datatype Mapping 8-25

Using Package DEBUG_EXTPROC 8-51
Demo Program 8-51
Guidelines for External C Procedures 8-51
Restrictions on External C Procedures 8-53
Part III The Active Database
9 Using Triggers
Designing Triggers 9-2
Creating Triggers 9-2
Types of Triggers 9-3
Overview of System Events 9-4
Getting the Attributes of System Events 9-4
Naming Triggers 9-4
When Is the Trigger Fired? 9-5
Do Import and SQL*Loader Fire Triggers? 9-5
How Column Lists Affect UPDATE Triggers 9-6
Controlling When a Trigger Is Fired (BEFORE and AFTER Options) 9-6
xviii
Ordering of Triggers 9-7
Modifying Complex Views (INSTEAD OF Triggers) 9-8
Views that Require INSTEAD OF Triggers 9-9
INSTEAD OF Trigger Example 9-10
Object Views and INSTEAD OF Triggers 9-11
Triggers on Nested Table View Columns 9-12
Firing Triggers One or Many Times (FOR EACH ROW Option) 9-13
Firing Triggers Based on Conditions (WHEN Clause) 9-14
Coding the Trigger Body 9-15
Example: Monitoring Logons with a Trigger 9-15
Example: Calling a Java Procedure from a Trigger 9-16
Accessing Column Values in Row Triggers 9-17
Example: Modifying LOB Columns with a Trigger 9-18

Derived Column Values and Triggers: Example 9-46
Building Complex Updatable Views Using Triggers: Example 9-47
Tracking System Events Using Triggers 9-49
Fine-Grained Access Control Using Triggers: Example 9-49
CALL Syntax 9-50
Responding to System Events through Triggers 9-50
10 Working With System Events
Event Attribute Functions 10-2
List of Database Events 10-7
System Events 10-7
Client Events 10-8
11 Using the Publish-Subscribe Model for Applications
Introduction to Publish-Subscribe 11-2
Publish-Subscribe Architecture 11-3
Publish-Subscribe Concepts 11-3
Examples of a Publish-Subscribe Mechanism 11-6
Part IV Developing Specialized Applications
12 Using Regular Expressions With Oracle Database
What are Regular Expressions? 12-2
Oracle Database Regular Expression Support 12-2
Oracle Database SQL Functions for Regular Expressions 12-2
Metacharacters Supported in Regular Expressions 12-4
Constructing Regular Expressions 12-5
xx
Basic String Matching with Regular Expressions 12-5
Regular Expression Operations on Subexpressions 12-5
Regular Expression Operator and Metacharacter Usage 12-5
13 Developing Web Applications with PL/SQL
PL/SQL Web Applications 13-2
PL/SQL Gateway 13-3

Page Directive 13-27
Procedure Directive 13-27
Parameter Directive 13-28
Include Directive 13-28
Declaration Block 13-28
Code Block (Scriptlet) 13-28
Expression Block 13-29
Loading the PL/SQL Server Page into the Database as a Stored Procedure 13-29
Running a PL/SQL Server Page Through a URL 13-30
Sample PSP URLs 13-30
Examples of PL/SQL Server Pages 13-31
Sample Table 13-31
Dumping the Sample Table 13-32
Printing the Sample Table using a Loop 13-32
Allowing a User Selection 13-33
Sample HTML Form to Call a PL/SQL Server Page 13-35
Debugging PL/SQL Server Page Problems 13-38
Putting an Application using PL/SQL Server Pages into Production 13-39
Enabling PL/SQL Web Applications for XML 13-41
14 Porting Non-Oracle Applications to Oracle Database 10g
Performing Natural Joins and Inner Joins 14-2
Migrating a Schema and Data from Another Database System 14-2
Performing Several Comparisons within a Query 14-2
15 Using Flashback Features
Overview of Flashback Features 15-2
Application Development Features 15-2
Database Administration Features 15-3
Database Administration Tasks Before Using Flashback Features 15-4
Using Flashback Query (SELECT AS OF) 15-5
Examining Past Data: Example 15-6

Using OCI with the Oracle XA Library 16-18
Transaction Control using XA 16-19
Examples of Precompiler Applications 16-20
Migrating Precompiler or OCI Applications to TPM Applications 16-21
XA Library Thread Safety 16-23
Specifying Threading in the Open String 16-23
Restrictions on Threading in XA 16-23
xxiii
Troubleshooting XA Applications 16-24
XA Trace Files 16-24
The xa_open string DbgFl 16-24
Trace File Locations 16-25
Trace File Examples 16-25
In-Doubt or Pending Transactions 16-26
Oracle Database SYS Account Tables 16-26
XA Issues and Restrictions 16-27
Changes to Oracle XA Support 16-32
XA Changes from Release 8.0 to Release 8.1 16-32
XA Changes from Release 7.3 to Release 8.0 16-32
Session Caching Is No Longer Needed 16-33
Dynamic Registration Is Supported 16-33
Loosely Coupled Transaction Branches Are Supported 16-33
SQLLIB Is Not Needed for OCI Applications 16-34
No Installation Script Is Needed to Run XA 16-34
XA Library Use with Oracle Real Application Clusters Option on All Platforms 16-34
Transaction Recovery for Oracle Real Application Clusters Has Been Improved 16-34
Both Global and Local Transactions Are Possible 16-34
The xa_open String Has Been Modified 16-35
Index
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