Oracle10g PL/SQL Programming V1.0

Transcription

1 Oracle10g PL/SQL Programming V1.0

2 Oracle10g PL/SQL Programming SkillBuilders, Inc. 24 Salt Pond Road, Unit C-4 South Kingstown, RI Author: David G. Anderson Legal Notice Copyrights Copyright All rights reserved. Printed in the United States of America. No part of this publication may be reproduced, distributed or displayed in any form or by any means, or stored in a database, retrieval system or other media without the prior written permission of SkillBuilders, Inc. Trademarks The product/service names mentioned herein are manufacturer/publisher trademarks and are used only for purposes of identification. Microsoft, Microsoft Windows 95, Microsoft Windows 98, Microsoft Windows NT, and Microsoft Windows XP are registered trademarks of Microsoft Corporation. Netscape, Netscape Navigator, and the Netscape logo are registered trademarks of Netscape Communications Corporation in the United States and other countries. Oracle, Oracle8i, Oracle9i and Oracle10g are registered trademarks of Oracle Corporation. All other brand, product and service names are the trademarks of their respective companies or owners as mentioned herein. Disclaimer Information within this publication is subject to change without notice. Although every precaution has been taken in the preparation of this book, the publisher and author assume no responsibility for errors or omissions. The author and SkillBuilders, Inc. make no representation or warranty with respect to the contents herein and specifically disclaims any implied warranties of fitness for any particular purpose. SkillBuilders, Inc. disclaims all liability for any direct, indirect, incidental or consequential, special or exemplary damages resulting from the use of the information in this document or from the use of any products described in this document. Copyright Reproduction is strictly prohibited.

3 Oracle10g PL/SQL Programming Workshop 3 days Description This class will teach you how to write efficient and scalable PL/SQL programs to create database-intensive PL/SQL applications. You will learn the critical and fundamental aspects of PL/SQL language. Learning how to create efficient, scalable PL/SQL programs is an important objective of this course. To meet that objective, the course includes instruction on such things as the proper use of bind variables, bulk processing, pipelining, benchmarking different formulations of a routine and profiling PL/SQL programs to identify the code that should be tuned. Hands-on workshops constitute approximately 50% of the class. As with all of our courses, this class is highly customizable to your specific training requirements. Audience Prerequisites Next Courses Objectives Developers and Analysts. Database Administrators who know a programming language will also benefit. You must possess strong programming skills to benefit from this class. (We will not teach you the basics of programming such as logic flow and conditional logic. We will, however, teach you how to do it efficiently in PL/SQL.) Experience with a procedural language (e.g. Java, C or COBOL), SQL and SQL*Plus is required. Advanced PL/SQL Programming, Advanced Queries for Oracle10g Databases, Oracle10g SQL Tuning for Developers and DBA s, Oracle10g Database Administration After successfully completing this course, you will be able to: Code efficient, scalable PL/SQL programs that include common programming constructs such as data-typing, variable assignment, flow control, cursor handling, bulk processing, array processing and error handling Create PL/SQL stored procedures that accept and return values or sets of values Manage stored procedure dependencies and privileges Create PL/SQL functions, including powerful table functions and pipelined table functions Create database triggers for auditing, complex business rule support, simple replication and more Create and maintain simple Oracle packages Use the UTL_FILE package to read and write to operating system files. Use the UTL_MAIL package to send from an Oracle database Use the DBMS_PROFILER package to profile and tune PL/SQL programs Do simple benchmarking of PL/SQL code with the DBMS_UTITLITY package Copyright 2006 SkillBuilders V1.0

4 Oracle10g PL/SQL Programming Page i 1. Introduction to PL/SQL Lesson Objectives What is PL/SQL? Why Use PL/SQL? PL/SQL Program Structure Anonymous Blocks Compile Errors Output to SQL*Plus Procedures Procedure Compile Errors Functions Packages Data Dictionary Triggers Tools for Development Working in SQL*Plus Introduction to PL/SQL Workshops Language Fundamentals Lesson Objectives Statements PL/SQL Symbols Quoting Mechanism Common PL/SQL Datatypes Declaring Variables %TYPE PL/SQL Records Records: %ROWTYPE Programmer Defined Records Language Fundamentals Workshop A Variable Scope Nested Blocks Functions Regular Expressions IF Statement CASE Simple CASE Searched CASE Simple Loops Nested Loops Numeric FOR Loop PL/SQL Arrays

5 Oracle10g PL/SQL Programming Page ii Simple Array Example Array Methods Language Fundamentals Workshop B PL/SQL and SQL: Basics Lesson Objectives SELECT INTO Statement Implicit Cursor Loops Basics Workshop A (Cursor Loop) DML in PL/SQL Cursor Attributes Embedding DDL Basics Workshop B (NDS) PL/SQL and SQL: Cursors Lesson Objectives What is a Cursor? Cursor Processing Cursor Attributes Cursors Workshop A Dynamic Cursors Dynamic Cursor Example Variable Scope & Cursors Problem Example Cursor Parameters Cursor Record Cursor FOR LOOP Cursor FOR LOOP Example Cursors Optional Workshop B Referencing the Current Row FOR UPDATE Example Cursors Optional Workshop C PL/SQL and SQL: Bulk Processing Lesson Objectives Bulk Processing Bulk Collect Bulk Collect: Multiple Rows Bulk Collect: Multiple Arrays Bulk Collect: Array of Records Bulk Collect: FETCH with LIMIT Bulk Processing Workshop A...5.9

6 Oracle10g PL/SQL Programming Page iii Bulk DELETE Bulk INSERT g FORALL Improvements Returning into Arrays Summary Bulk Processing Workshop B Procedures Lesson Objectives What is a Procedure? Abbreviated Syntax Simple Example Review: Compile Errors Compiler Warnings Procedure Signatures Calling Procedures Procedure Synonyms Referencing Parameters by Name Returning Sets: REF CURSOR Dropping Procedures Dependencies ALTER COMPILE Privileges Execute Privilege The Data Dictionary Procedures Workshop Functions Lesson Objectives What is a Function? Abbreviated Syntax Simple Example Calling Functions The Data Dictionary Functions Workshop A Table Functions Building a Table Function Using a Table Function Pipelined Functions Pipelined Example Test Data Generator Functions Workshop B

7 Oracle10g PL/SQL Programming Page iv 8. Error Handling Lesson Objectives Types of Errors Runtime Errors Exception Concepts Predefined Named Exceptions Syntax Handling Exceptions Recovering from Errors Logging Exceptions Debugging with FORMAT_ERROR_BACKTRACE RAISE_APPLICATION_ERROR RAE Example Error Handling Workshop Raising Exceptions Raising User Exceptions EXCEPTION_INIT Summary Packages Lesson Objectives Concepts Package Benefits Package Benefits Diagram Package Contents Package Specification Syntax Package Specification Example Package Body Syntax Package Body Example Privileges Calling Packaged Objects Initialization Code Session Variables Package Body Variables Packages Workshop A Package Overloading Overloading Example Packages Workshop B Compiling Packages DROP Package Packages Workshop C Supplied Packages Summary

8 Oracle10g PL/SQL Programming Page v 10. Triggers Lesson Objectives Trigger Concepts Trigger Execution Create Trigger Syntax Row Trigger :OLD Reference Variable :NEW Reference Variable Trigger Attributes Audit Trigger Derived Value Trigger Restrictions Security Privileges Triggers Workshop A Table Trigger Triggers Workshop B Autonomous Transactions Autonomous Trigger Triggers Workshop C INSTEAD OF Triggers Triggers Workshop D File I/O Using UTL_FILE Lesson Objectives UTL_FILE Concepts Setup Unix File Permissions Opening Files Closing Files Reading Files Reading Files Example Writing Files Writing Files - PUT Writing Files - PUT_LINE Writing Files - NEW_LINE Writing Files - PUTF Writing Files Example UTL_FILE Workshop Using DBMS_JOB Lesson Objectives What is DBMS_JOB?

9 Oracle10g PL/SQL Programming Page vi Setup DBMS_JOB.SUBMIT SUBMIT Example Running a Job Cleaning Up Broken Jobs Removing a Job Changing Job Parameters Viewing Job Information Using DBMS_JOB Workshop Profile and Tune Lesson Objectives Introduction to Tuning PL/SQL DBMS_PROFILER Profiler Setup Using Profiler Testing Reporting Benchmarking Profile & Tune PLSQL Workshop Miscellaneous 10g Enhancements Lesson Objectives Performance: Compiler Optimization Comparison Native Compilation Review Native Compilation: New Stuff Conditional Compilation Introducing UTL_MAIL UTL_MAIL SET UP UTL_MAIL EXAMPLE Nested Table Enhancements New and Revised Packages Lesson Summary

10 Introduction to PL/SQL 1.1 Lesson 1 Introduction to PL/SQL A programmer s introduction to the what, why, when and where of PL/SQL. SKILLBUILDERS

11 Introduction to PL/SQL Lesson Objectives What is PL/SQL? What is it good for? Basic structure of a PL/SQL program Simple examples of common PL/SQL objects Anonymous block Procedure Function Package Trigger Tips for working in SQL*Plus In-depth lessons dedicated to these subjects later in this course

12 Introduction to PL/SQL 1.3 What is PL/SQL? 1.3 PL/SQL = Procedural Language extensions for SQL Proprietary language for Oracle database 3 rd generation procedural language variable definition, assignment conditional processing IF and CASE looping constructs error handling Seamless integration of SQL, SQL functions PL/SQL is a procedural language for the ORACLE database. PL/SQL stands for Procedural Language extensions to SQL. It is a proprietary language; i.e. a PL/SQL program will not run on a SQL Server database. As a 3 rd generation language, it provides many of the standard capabilities you would expect including: Variable definition and assignment Conditional processing (IF and CASE statements) Loop constructs Error handing It provides seamless integration (embedding) of SQL and SQL functions. Note that Oracle client-side products such as Oracle Forms also support PL/SQL.

13 Introduction to PL/SQL 1.4 Why Use PL/SQL?... Efficient data manipulation Good for lots of SQL, limited procedural code Tight integration with SQL Embed in PL/SQL statements Lots of work done automatically Open / close queries and cursors Compatible datatypes No conversions Not great for lots of complex procedural code However, consider Native Compilation 1.4 Because of the tight integration of SQL and PL/SQL, PL/SQL is very good at data manipulation. So if you are coding a routine that contains lots of SELECT, UPDATE, DELETE and INSERT statements, with relatively little procedural code, PL/SQL is a good choice. In this course you will see how PL/SQL does many things automatically for you; e.g. open and close cursors. Conversely, if you writing complex procedural code that will be repeatedly executed, Java or C might be a better choice. However, with the PL/SQL Native Compilation feature, PL/SQL is becoming a consideration even for computationally intensive routines.

14 Introduction to PL/SQL Why Use PL/SQL? Simple language Learn quickly Only need SQL*Plus to develop & deploy Portable within Oracle database No code change to migrate to another Oracle server Even on different platform Callable from any client Java,.NET, COBOL Anyone who can connect to DB can call 1.5 PL/SQL is relatively simple to learn and you ll only need SQL*Plus to develop, test and deploy PL/SQL programs. PL/SQL programs are portable to any Oracle database running on any platform. Rarely, if ever, will code changes be required. An exception would be if specific OS paths or commands are hard-coded within a program. PL/SQL programs are callable from any type of client. If the client can connect to the database, it can call a PL/SQL procedure or function and that procedure can return a value or result set to the caller.

15 Introduction to PL/SQL 1.6 PL/SQL Program Structure 1.6 PL/SQL is a block-structured language 3 possible blocks Only BEGIN block required Declarative Executable Error Handling DECLARE variables; constants; cursors; BEGIN BEGIN PL/SQL and and SQL SQL statements; EXCEPTION exception handlers; END; END; Terminate each statement or declaration with semi-colon PL/SQL is a block-structured language. Each PL/SQL program consists of up to 3 sections, or blocks. The declarative block contains all declarations for variables, constants and cursors. The BEGIN block contains the main body of PL/SQL and SQL statements; it is the only required section. Finally, the exception block is where all errors (exceptions in PL/SQL) can be trapped and resolved, i.e. handled. Each declaration or statement must end in a semicolon.

16 Introduction to PL/SQL 1.7 Anonymous Blocks Execute block from SQL*Plus SQL> 3 SQL> SQL> declare 2 v_custno number := := &1 &1 ; 3 begin begin 4 INSERT INTO INTO cust_history 5 SELECT * 6 FROM FROM customer 7 WHERE WHERE cust_no = v_custno; 8 end; end; 9 / old old 2: 2: v_custno number := := &1 &1 ; new new 2: 2: v_custno number := := 3 ; PL/SQL procedure successfully completed. Don t forget the slash Seamless integration of SQL Copy customer to the history table 1.7 Anonymous Blocks are called anonymous because they are not stored on the database thus they do not have a name. They are also sometimes referred to as unnamed blocks. However, as this example illustrates, they can be stored in an operating system file ( COPYCUST.SQL ) Anonymous blocks are usually executed under SQL*PLUS to: update table data produce reports build database objects Typically, the code for an anonymous block is placed in a.sql script file. Note that we follow our anonymous block with a slash (/) on a line by itself. When we run the script from SQL*Plus (with the at sign), the anonymous block is read into the SQL*Plus buffer and scanned for SQL*Plus substitution variables. The slash tells SQL*Plus to send the contents of the SQL*Plus buffer to the server for execution. Note that the SQL*Plus buffer can hold one and only one SQL command or PL/SQL block. I have used a SQL*Plus substitution variable in place of the hard coded customer number. Thus, in this case, this PL/SQL block must be executed from SQL*Plus. Only SQL*Plus understands SQL*Plus substitution variables! SQL*Plus Tips Optionally, use SET ECHO OFF to suppress the display of the anonymous block when executed from the SQL*Plus command prompt. Optionally, use SET VERIFY OFF to suppress the display of the old and new substitution messages. Supplemental Notes Note that the example shown here is for educational purposes only specifically to illustrate the block structure of a PL/SQL program. The SQL statement within the BEGIN block could more easily be executed without being coded within the confines of a PL/SQL block.

17 Introduction to PL/SQL 1.8 Compile Errors 1.8 SQL> 6 * will be INSRET INTO INTO cust_history somewhere near * clause that caused ERROR ERROR at at line line 4: error 4: ORA-06550: line line 4, 4, column 10: 10: PLS-00103: Encountered the the symbol "INTO" when when expecting one one of of the the following: := :=. % ; ORA-06550: line line 8, 8, column 1: 1: PLS-00103: Encountered the the symbol "END" "END" While the error message has identified the correct line (line 4 contains INSERT spelled incorrectly), note the misleading error message. Later we will see that compile errors in triggers, stored procedures, and stored functions are not automatically displayed by SQL*Plus. You must specifically display them yourself with the SQL*Plus SHOW ERRORS command.

18 Introduction to PL/SQL 1.9 Output to SQL*Plus Use DBMS_OUTPUT.PUT_LINE to display text on screen SQL> SQL> set set serveroutput on on SQL> SQL> begin begin 2 dbms_output.put_line('hello World') ; 3 end end ; 4 / Hello Hello World World PL/SQL procedure successfully completed. 1.9 PL/SQL may display output to SQL*Plus by using the Oracle supplied package procedure called DBMS_OUTPUT.PUT_LINE. This procedure displays text on the output device (console) in SQL*Plus. In order for the output from DBMS_OUTPUT.PUT_LINE to be seen, the SET SERVEROUTPUT on SQL*Plus command must be executed. You may want to consider putting this command in your LOGIN.SQL file as this setting reverts to the default (off) when the session ends.

19 Introduction to PL/SQL 1.10 Procedures 1.10 SQL> SQL> SQL> create procedure p1 p1 as as 2 begin begin 3 dbms_output.put_line('hello World'); 4 end; end; 5 / Procedure created. SQL> SQL> exec exec p1 p1 Hello Hello World World Call the procedure PL/SQL procedure successfully completed. with the SQL*Plus EXECUTE command Procedure is now compiled and stored in database Procedures and functions are callable subprograms which are also compiled and stored permanently in the Oracle server. (The main difference between procedures and functions is that stored functions must return a value to the caller. Otherwise, they are basically the same. You will learn much more about this later in this course.) In the example shown above, I coded a simple stored procedure in file PROCEDURE1.SQL. The procedure is created with the CREATE PROCEDURE statement (refer to the Oracle9i SQL Reference for more information on this statement; you will learn a lot more about this statement later in this course). When I run the file, it compiles and stores the stored procedure in the database. Note that the name of the procedure is p1 ; the name of the OS file that contains the source code is PROCEDURE1.SQL. I use the SQL*Plus EXECUTE command ( exec p1 ) to call the stored procedure.

20 Introduction to PL/SQL 1.11 Procedure Compile Errors Drop procedure SQL> SQL> drop drop procedure p1; p1; before trying to Procedure dropped. recreate, or use or replace on create SQL> SQL> SQL> create procedure p1 p1 as as 2 begin begin 3 dbms_output.put_line('hello World') 4 end; end; 5 / Warning: Procedure created with with compilation errors. SQL> SQL> show show errors Use the SQL*Plus Errors for for PROCEDURE P1: P1: SHOW ERRORS command LINE/COL ERROR ERROR /1 4/1 PLS-00103: Encountered the the symbol "END" "END" when when expecting 1.11 Compile errors generated by the CREATE PROCEDURE (and CREATE FUNCTION, CREATE TRIGGER) statements are not automatically displayed on the SQL*Plus screen. These errors are stored in a data dictionary view called USER_ERRORS. They can be displayed by querying this view or, as shown in this slide, by using the SQL*Plus SHOW ERRORS command. The complete text of the error message is: LINE/COL ERROR /1 PLS-00103: Encountered the symbol "END" when expecting one of the following: :=. ( % ; The symbol ";" was substituted for "END" to continue. The problem is a missing semi-colon at the end of line 3. Notes continue on the next page

21 Introduction to PL/SQL 1.12 Supplemental Notes Note that instead of using DROP PROCEDURE you can add the OR REPLACE option to the CREATE PROCEDURE command: SQL> create or replace procedure p1 as 2 begin 3 dbms_output.put_line('hello World'); 4 end; 5 / Procedure created. The DROP statement can be used to drop most Oracle procedural objects, e.g. DROP FUNCTION, DROP TRIGGER, DROP PACKAGE, DROP PACKAGE BODY etc.

22 Introduction to PL/SQL 1.13 Functions 1.13 SQL> SQL> SQL> create or or replace function f1 f1 2 return char char 3 as as 4 begin begin 5 return ('test'); 6 end; end; 7 / Function created. Must identify datatype function will return Call function from an SQL or PL/SQL statement SQL> SQL> select f1() f1() from from dual; dual; F1() F1() test test A PL/SQL function is very similar to a procedure; it is just that the function always returns a value to the caller and is invoked semantically different from the procedure. Whereas the procedure invocation is a statement in itself, the function is called within the context of another PL/SQL or SQL statement.

23 Introduction to PL/SQL 1.14 Packages Package is a group of PL/SQL objects SQL> SQL> create or or replace package p1 p1 as as 2 function f1 f1 return char; char; 3 procedure proc1; 4 end; end; SQL> 5 / SQL> create or or replace package body body p1 p1 as as 2 function f1 f1 return char char 3 Package created. as as 4 begin begin 5 return ('test'); 6 end; end; 7 8 procedure proc1 proc1 as as 9 begin begin dbms_output.put_line('hello World'); end; end; end; end; / A package is a group of PL/SQL objects often including procedures and functions. There are many benefits of packaging, which we will discuss in a subsequent lesson dedicated to packages. For now, it is just important to understand that PL/SQL objects can be packaged as opposed to standalone objects. Refer to the supplied script PACKAGE1.SQL for a working copy of the code shown here.

24 Introduction to PL/SQL Packages Qualify packaged objects with package name 1.15 SQL> SQL> select p1.f1 p1.f1 from from dual; dual; F1 F test test A packaged object is referenced by its package name, as shown above.

25 Introduction to PL/SQL 1.16 Data Dictionary Dictionary records existence of PL/SQL objects SQL> SQL> select object_name, object_type from from user_objects 2 where where object_type in in ('PROCEDURE', 'FUNCTION'); OBJECT_NAME OBJECT_TYPE F1 F1 FUNCTION P1 P1 PROCEDURE 1.16 The existence of PL/SQL objects (procedures, functions, packages, etc) is recorded in the data dictionary. USER_OBJECTS contains one row for each object.

26 Introduction to PL/SQL 1.17 Triggers Code tied to a table Executes automatically when DML executes SQL> SQL> SQL> create trigger customer_name 2 before update or or insert on on customer 3 for for each each row row 4 begin begin 5 /* /* convert character values to to upper upper case case */ */ 6 :new.lastname := := upper( :new.lastname ); ); 7 :new.firstname := := upper( :new.firstname ); ); 8 dbms_output.put_line('trigger fired'); 9 end; end; / Trigger created. Trigger tied to CUSTOMER table Use the UPPER function to convert characters inserted into the database Triggers are, usually, code associated with a table and are executed automatically when an appropriate SQL statement is issued against the table. There are also triggers which are associated with system events such as Startup and Shutdown or DDL such as CREATE and DROP statements. Other triggers can be created which are associated with user events such as Logon or Logoff. Triggers are compiled and stored permanently in the Oracle server. Triggers are often used to: Enforce complex business and/or integrity rules Audit modifications to a table Derive column values Maintain mirror tables This trigger, called customer_name, will execute whenever an INSERT or UPDATE statement is executed on the DAVE.CUSTOMER table (the schema of the compiler is used for the table, unless qualified or a synonym exists).

27 Introduction to PL/SQL Triggers 1.18 SQL> SQL> insert into into customer 2 (cust_no, firstname, lastname) 3 values 4 (3423, 'dave', 'anderson'); trigger fired fired Verification that trigger executed 1 row row created. SQL> SQL> select firstname, lastname 2 from from customer 3 where where cust_no = 3423; 3423; FIRSTNAME LASTNAME DAVE DAVE ANDERSON Characters are converted to upper case We see that the PUT_LINE procedure displayed the text trigger fired when the INSERT statement executed. This is purely diagnostics. And we see that the trigger did indeed work; the characters have been converted to upper case characters. Refer to the supplied script TRIGGER1.SQL for a copy of the code shown in this example.

28 Introduction to PL/SQL Tools for Development SQL*Plus is a common tool Included with all Oracle database products Procedure Builder Sophisticated IDE GUI tool An extra cost product Sophisticated debugging features Breakpoints stepping through code variable examination, etc. TOAD Developer and DBA tool SQL*Plus is the traditional tool for PL/SQL development as it is included with all versions of the Oracle database. You may choose to use a more robust development tool, like Procedure Builder, which provides a graphical development environment. This product has to be purchased separately but may be worth the extra cost as it provides many sophisticated debugging features and a better overall working environment for your development efforts. There are many third party tools also available such as TOAD from Quest Software. Free limited feature versions of this product are available at

29 Introduction to PL/SQL Working in SQL*Plus SET ECHO ON Show compiled source on your screen SET SERVEROUTPUT ON PUT_LINE calls will be displayed after program returns control to SQL*Plus Put in LOGIN.SQL SHOW ERRORS Error messages will refer to a line and column number Oracle Error messages manual is available to help Debugging your PL/SQL programs can be tedious if you are uncertain of where the error messages are pointing to. The simplest way to see the errors is to SET ECHO ON prior to the compile of your source. You will have the program source echoed on your screen with line numbers. If there are any error messages, it will be simple to ascertain where the error occurred. (You can also get the source line number from your USER_SOURCE library. You cannot just count lines in your original source file because the PL/SQL compiler does not count blank lines and some comment lines.) I recommend that you put the SET ECHO ON and SERT SERVEROUTPUT commands in your LOGIN.SQL file. This file, when placed in your working directory, will be automatically executed when you start SQL*Plus. Refer to the sample LOGIN.SQL file supplied with this course for and example. For anonymous blocks, the error will be displayed when you try to execute the code. For procedures, functions, packages and triggers, remember to use the SHOW ERRORS command to display the error messages.

30 Introduction to PL/SQL 1.21 Introduction to PL/SQL Workshops 1.21 Hello World Setup Workshop Hello World 1. No course is complete without the infamous Hello World! application. So let s create an anonymous PL/SQL block to print the string Hello World! to the screen. Code the PL/SQL block in a script, and test it by running the script. 2. Convert the anonymous block into a stored procedure. Compile and test the procedure. 3. Convert the stored procedure into a function. Compile and test the function. 4. Drop your standalone versions of your procedure and function. Package and test the packaged versions. Workshop Setup Run the supplied scripts DDL.SQL and INSERT.SQL to create a series of test tables that will be needed as you progress through the rest of the course.

31 Language Fundamentals 2.1 Lesson 2 Language Fundamentals A programmer s introduction to the fundamental language elements in PL/SQL. SKILLBUILDERS

32 Language Fundamentals Lesson Objectives Statements Symbols Datatypes Variable declaration and assignment Declaring PL/SQL Records Variable scope Nested Blocks IF CASE Looping constructs Introduction to Arrays To some extent, this is a reference chapter. You ll see relatively large lists of statements, datatypes and symbols. I recommend that you do not attempt to remember each one as you progress through this chapter. We ll incorporate them into examples in the remainder of the course. However, do use this lesson to acquire a solid grasp of the basic format of the IF, CASE, loop statements, and a good understanding of arrays. But here again, you ll see these statements used throughout the rest of the course.

33 Language Fundamentals PL/SQL CASE := IF LOOPs EXIT TYPE FORALL OPEN FETCH CLOSE CURSOR procedure_call; EXECUTE IMMEDIATE RETURN RAISE NULL GOTO Statements SQL SELECT INTO INSERT DELETE UPDATE LOCK TABLE MERGE CASE ROLLBACK SAVEPOINT SET TRANSACTION Pragmas AUTONOMOUS_ TRANSACTION EXCEPTION_INIT RESTRICT_ REFERENCES Mini-Workshop Shown here is a list of commonly used statements that can be used within a PL/SQL program. Refer to the Oracle9i PL/SQL User's Guide and Reference for a complete list and description of each statement. Throughout the remainder of this course you will learn the purpose of and see examples of many of these statements. You may be wondering, where are the rest of the SQL statements? DDL statements such as CREATE, GRANT, DROP etc. Well, these are DDL statements and cannot be coded directly within PL/SQL. Use the EXECUTE IMMEDIATE statement to embed DDL statements. Mini-Workshop Access chapter 13 of the Oracle9i PL/SQL User's Guide and Reference (R2) and review the examples of the following LOOP statements: basic_loop_statement for_loop_statement cursor_for_loop_statement Access to the complete set of Oracle manuals is free at

34 Language Fundamentals 2.4 Symbol PL/SQL Symbols Purpose + - * / Addition, Subtraction, Multiplication, Division := Assignment operator = Equal to relation >, < Greater than/less than relation <= >= Less than/greater than or equal to <>!= ~= ^= Not equal operators ; Statement terminator, Item separator Quoted identifier ' Character string identifier -- Single line comment. /* */ Beginning / ending of multi-line comment List List continues 2.4 PL/SQL symbols continued: Symbol Purpose. Component selector ( ) Used to control precedence. 5* (2+2) % Prefix for PL/SQL attributes. emp.name%type.. Range operator for loops. FOR x in 1..5 Used to reference remote databases. select * from emp@hq; : Used to prefix a host variable. => The arrow. Use in procedure calls to assign value to a parameter. Concatenation operator. << >> Label. Refer to chapter 2 of the Oracle9i PL/SQL User s Guide and Reference for complete details on the PL/SQL symbols (see delimiters ).

35 Language Fundamentals Quoting Mechanism 10g Like SQL, PL/SQL supports a new technique for denoting quotes LINUX> declare 2 v1 v1 varchar2(100); 3 begin begin 4 v1 v1 := := q'[peg's birthday present]'; 5 insert into into t values(v1); 6 end; end; 7 / PL/SQL procedure successfully LINUX> completed. select * from from t; t; C1 C Peg's Peg's birthday present Oracle10g introduces a new technique for identifying enclosing quotes (delimiters) in text literals. It is supported in SQL statements and PL/SQL statements. This makes coding strings that contain single quotation marks cleaner and less error-prone. Use the letter q (not case-sensitive) followed by the open quote and the quote delimiter character. The Oracle10g SQL Reference states that the quote delimiter character can be any character; however, I find it easiest to use a character that is not used in the literal itself. If the quote delimiter character is [, {, <, or (, then the closing delimiter must be ], }, > or ), respectively. Otherwise use the same exact character as the opening and closing quote delimiter character. Refer to the section on Literals in the Oracle10g SQL Reference manual for more information on what Oracle calls the alternative quoting mechanism.

36 Language Fundamentals Common PL/SQL Datatypes number[(precision,scale)] char[(length)] varchar2(length) date timestamp timestamp with time [local] zone boolean ref cursor exception record table raw(length) long raw long blob clob nclob bfile rowid PL/SQL datatypes define the format of a variable, constant or parameter (parameters are used to pass values to and from a procedure or function). The slide contains a list of commonly used PL/SQL datatypes. In addition to the examples throughout the remainder of this course, refer to Chapter 3 of the PL/SQL User s Guide and Reference for a complete list and description of the datatypes. Here is a brief description of the datatypes listed here: NUMBER. Specify number of digits (precision) and number of decimal places (scale) if you want to store fixed point numbers. Omit precision and scale for floating point numbers. NUMBER has many subtypes such as DECIMAL and INTEGER; refer to the Oracle documentation for more information. CHAR is fixed length character data. The default length of a CHAR variable is 1, the maximum length is The database character set determines the internal representation. VARCHAR2 is variable length character data. Maximum length is For better performance, Oracle pre-allocates 2000 bytes of storage for all VARCHAR2 definitions less than 2000 bytes (it eliminates reallocations as different sized strings are allocated to it, Tom Kyte, May 2004, DATE holds a date/time value. TIMESTAMP contains a date/time value with fractional microseconds. Notes continue on the next page

37 Language Fundamentals 2.7 TIMESTAMP WITH TIME ZONE adds a time zone component to a TIMESTAMP type. BOOLEAN variables contains TRUE, FALSE, or NULL and are use in conditional logic, e.g. CASE and IF statements. e.g. IF VALID_ORDER THEN. EXCEPTION is used to define a user-defined exception name, for example customer_not_found. Refer to the Error Handling lesson for more information. REF CURSOR is a pointer to a memory cursor. Useful for returning sets of rows to callers / clients. RECORD defines a composite type; a collection of other scalar or composite types. TABLE defines a PL/SQL unbounded array, officially called an index-by table or associative array. Refer the examples later in this lesson for more information. RAW and LONG RAW are binary data. LONG RAW has been deprecated in favor of BLOB. BLOB is best to use for large binary objects. LONG and CLOB are large character data objects, better to use newer CLOB. NCLOB is national character set long character object. BFILE is an external binary file. ROWID is a pointer to a table row.

38 Language Fundamentals 2.8 Declaring Variables Specify the following: name datatype nullability (optional) Variable name name is is not notcase sensitive initial value (optional) SQL> declare 2 v_lastname varchar2(20) not not null := := 'SMITH'; 3 begin 4 If If V_Lastname = 'SMITH' then null; end end if; if; 5 end; 6 / NULL NULL is is the the no-op no-op statement PL/SQL procedure successfully completed. Comparison is is case case sensitive Initial Initial value value 2.8 Variables are declared in the DECLARE section of the program. Required are name and datatype. The name, like all Oracle names, must follow these rules: 1 30 alpha-numeric characters 1 st character must be alphabetic Valid special characters are _, $ and # Avoid reserved words such as SELECT In this example, V_LASTNAME is defined with the NOT NULL clause, so it can not contain a null value. An exception is raised if an initial value is not assigned (see the next page for an example). Therefore we must assign the variable an initial value ('SMITH in this example). This is done with the assignment operator (:=) or the DEFAULT keyword. NULL is the PL/SQL no-operation statement. I use it here (see line 4) simply because the BEGIN block is required, yet I do not want it to do anything I simply wanted to demonstrate the declaration and use of a variable. Notes continue on the next page

39 Language Fundamentals 2.9 An exception is raised if a variable defined as NOT NULL is not given a default value: SQL> declare 2 x number not null; 3 begin 4 null; 5 end; 6 / x number not null; * ERROR at line 2: ORA-06550: line 2, column 3: PLS-00218: a variable declared NOT NULL must have an initialization assignment

40 Language Fundamentals 2.10 Declaring Variables 2.10 SQL> SQL> declare 2 v_hiredate1 date; date; 3 v_hiredate2 date date := := sysdate; 4 v_total_sales number(8,2); 5 v_total_value1 number(8,2) := := 0; 0; 6 v_total_value2 number(8,2) default 0; 0; 7 v_order_valid boolean := := false; 8 v_lastname varchar2(20) not not null null := := 'Smith'; 9 c_co_name constant varchar2(20) := := 'SkillBuilders'; begin begin null; null; end; end; / PL/SQL procedure successfully completed. The examples define the following variables: 1. V_HIREDATE1 as a DATE object. The default value is NULL. 2. V_HIREDATE2 as a DATE initialized to the current date in SYSDATE. 3. V_TOTAL_SALES as a NUMBER that can hold 8 total digits with 2 digits after the decimal. Will accept range of values from to The default value in this variable is NULL. 4. V_TOTAL_VALUE1 as a NUMBER that can hold 8 total digits with 2 digits after the decimal. The default value is V_TOTAL_VALUE2 as a NUMBER that can hold 8 total digits with 2 digits after the decimal. The default value is also V_ORDER_VALID is a BOOLEAN initialized to FALSE. It can be used in CASE or IF statements, e.g. IF v_order_valid THEN 7. V_LASTNAME is a variable length character field up to 20 characters that cannot be NULL and is initialized to 'SMITH'. 8. C_CO_NAME is a CONSTANT. Constants have their values defined when the variable is defined, and the value not be changed (an exception occurs if an attempt is made to change the value). See the supplied script DECLARING_VARIABLES.SQL for a working copy of this example.

41 Language Fundamentals %TYPE SQL> declare 2 v1 v1 customer.lastname%type; 3 begin 4 select lastname into v1 v1 5 from customer 6 where cust_no = 1; 1; 7 dbms_output.put_line(v1); 8 end; 9 / Jones Datatype variable using using table table column column Use Use SELECT INTO INTO to to retrieve retrieve 1 row row PL/SQL procedure successfully completed. %TYPE is a great way to datatype a variable. Oracle will use the datatype of the table column, variable or cursor coded in the %TYPE specification. (You ll learn more about cursors later.) It is flexible; if the datatype changes, the new datatype will be picked up when the code is recompiled without a source code change. In this example variable V1 gets the same exact datatype as the LASTNAME column of the CUSTOMER table. This example includes the SELECT INTO statement (a form of implicit cursor). Some form of SELECT is required to access values in a database table (i.e. you cannot just compare to a table value in an IF or CASE statement without first selecting the data). You ll learn more about SELECT INTO and other means of retrieving data later in this course. See the supplied script TYPE.SQL for a copy of the code shown here.

42 Language Fundamentals 2.12 PL/SQL Records A record is a collection of related fields Similar structure to table row 4 ways to define records Table-based table-name%rowtype Programmer-defined Cursor-based cursor-name%rowtype Implicit with cursor FOR LOOP 2.12 These These are are discussed later later A PL/SQL record provides a way to deal with separate, but related, fields (variables) as a single unit. A record often has a similar structure to a row in a database table. There are four ways to define PL/SQL records. We will see examples of table-based and programmerdefined records in the following pages. See the supplied script DEFINING_PLSQL_RECORDS.SQL for examples of the four techniques for declaring variables.

43 Language Fundamentals 2.13 Records: %ROWTYPE 2.13 Define with %ROWTYPE Record matches row 9i supports record-based DML SQL> SQL> DECLARE 2 cust_rec customer%rowtype; 3 BEGIN BEGIN 4 cust_rec.cust_no := := 234; 234; 5 cust_rec.lastname := := 'Anderson'; 6 cust_rec.firstname := := 'Dave'; 7 INSERT INTO INTO customer 8 VALUES cust_rec; 9 END; END; / PL/SQL procedure successfully completed. A table-based record is defined with the %ROWTYPE attribute and creates a records that matches the structure of the table row. i.e., the record has the same number of fields as columns in the table and the fields have the same name and datatype. A PL/SQL record defined with %ROWTYPE: contains the same number of variables as columns in the table all datatypes match field names are the same as column names As we see in this example, the fields in the record are referenced with dot notation, for example cust_rec.lastname. Then we can use the entire record in the INSERT (and UPDATE) statements. As of Oracle9i, a table-based record is a convenient structure for DML operations. Note that the VALUES clause in the INSERT statement references the record eliminating the need to code each variable. The lack of parenthesis is correct syntax when a record is used. See the supplied script RECORDS.SQL for a working example of this code.

44 Language Fundamentals Programmer Defined Records... Define with the TYPE IS RECORD statement Each field explicitly defined Two steps Define record type with TYPE IS RECORD Define instance of record using type TYPE type_name IS IS RECORD (field1 datatype1 {NOT NULL} [:= [:= expr1], field2 datatype2 {NOT NULL} [:= [:= expr2]...); record_name type_name; A programmer defined PL/SQL record is a record where each field is explicitly defined by the programmer. You must first define a record type. Then, you must declare a variable of that type. The datatype of each field can be: Scalar types (NUMBER, VARCHAR2, DATE, etc.) %TYPE, %ROWTYPE or another programmer defined record (yes, Oracle supports nested records). Oracle objects (e.g. defined with CREATE TYPE object-name AS OBJECT) PL/SQL array (more on arrays later in this lesson). REF CURSOR, i.e. a pointer to a cursor. (more on REF CURSORS later in this lesson). Parameter descriptions: type_name Name of record type field Name of field (variable) in record datatype Datatype of field in record There is no limit on the number of fields within the record.

45 Language Fundamentals Programmer Defined Records CREATE OR OR REPLACE PACKAGE custpack AS AS TYPE TYPE cust_info_t IS IS RECORD (cust_no NUMBER, Package Package contains contains a first_purchase DATE DATE := := SYSDATE); record record type type END; END; / CREATE OR OR REPLACE FUNCTION create_cust RETURN custpack.cust_info_t Function Function returns returns IS IS a record record cust_rec custpack.cust_info_t; BEGIN BEGIN SELECT s1.nextval INTO INTO cust_rec.cust_no FROM FROM dual; dual; RETURN(cust_rec); END; END; / Example continues... This example shows that a programmer-defined record type can be packaged. Packaging the record makes the record global, i.e. accessible to any user with execute privilege on the package. Next, we see that a function can return a record see the RETURN(cust_rec) statement. (Later you will learn how to return sets of records!) Here, I have packaged a record type called CUST_INFO_T. Then, I use that type in a function called CREATE_CUST. The function returns a record. Note the reference to the TYPE within the function requires the prefix of the package name, as in CUSTPACK.CUST_INFO_T. This example requires that a sequence called S1 has been created, for example: CREATE SEQUENCE s1; See the supplied script RECORD_IN_PACKAGE.SQL for a working example of this code.

46 Language Fundamentals Programmer Defined Records Define record based on packaged TYPE Function call returns record SQL> SQL> declare 2 cust_rec custpack.cust_info_t; 3 begin begin 4 cust_rec := := create_cust(); 5 dbms_output.put_line(cust_rec.cust_no); 6 end; end; 7 / 1 PL/SQL procedure successfully completed. Define Define record record Call Call function function Here again we see the definition of a record based on a packaged TYPE. We also see the call to the function CREATE_CUST, where CREATE_CUST returns a record.

47 Language Fundamentals 2.17 Language Fundamentals Workshop A PL/SQL Records 2.17 Workshop PL/SQL Records 1. Code a function that accepts a customer number and returns a customer record populated with information about the customer. Use the SQL statement SELECT * INTO record FROM CUSTOMER WHERE cust_no = parameter to retrieve the customer row. 2. Code an anonymous block that calls the function and uses the PUT_LINE procedure to display one or more customer attributes.

48 Language Fundamentals Variable Scope Variables persist in block they are declared And any embedded sub-blocks Cannot be referenced in outer block Can use packages to create global or session variables if needed Easy to pass values Procedures can have IN and OUT parameters The scope of a variable is where it can be referenced (i.e. used or seen). When a variable is declared, it is accessible throughout the PL/SQL block and any embedded sub-blocks. A variable cannot be reference in: An outer (enclosing) block A called procedure or function (To accomplish this, use either use packaged variables or pass the procedure or function a value in the call. You will learn both techniques later in the course.) A calling procedure or function (To return a value from a procedure, use OUT type variables. Functions, by design, always return a value) (Using packages, we can create session (global) variables. This will be discussed in the lesson on packages later in this course.)

49 Language Fundamentals 2.19 Nested Blocks 2.19 SQL> SQL> declare 2 v_custno NUMBER := := 100; 100; 3 begin begin 4 dbms_output.put_line(v_custno) ; 5 declare 6 v_state CHAR(2):= 'NY' 'NY' ; 7 begin begin 8 dbms_output.put_line 9 (v_custno v_state) ; end end ; end end ; / NY 100NY Both Both variables variables can PL/SQL procedure successfully completed. can be be referenced referenced in in the the inner inner block block A PL/SQL variable can be referenced in blocks nested within the block in which the variable is defined unless the nested block contains a variable of the same name; then the local version of the variable is referenced. In the example, there are two blocks. In the first, we declare a variable, V_CUSTNO. In the second, we declare another variable, V_STATE. In the inner block, we can reference the V_CUSTNO variable. Take note that the V_STATE variable cannot be referenced outside the inner block. For instance, the following code will generate a compile error: declare v_custno NUMBER := 100; begin dbms_output.put_line(v_custno) ; declare v_state CHAR(2):= NY ; begin this reference dbms_output.put_line (v_custno v_state) ; end ; dbms_output.put_line(v_state) ; generates error end ; ERROR at line 10: ORA-06550: line 10, column 25: PLS-00201: identifier 'V_STATE' must be declared ORA-06550: line 10, column 4: PL/SQL: Statement ignored

50 Language Fundamentals 2.20 Functions 2.20 Most SQL functions can be used in PL/SQL statements 7 if if upper(v1) = 'ANDERSON' then then 8 null; null; 9 end end if; if; Specific PL/SQL error-reporting functions More More examples examples in in the the Error Error Handling Handling lesson lesson 7 v_msg v_msg varchar2(1020) default sqlerrm; 8 v_code number default sqlcode; Aggregate and analytic functions only in SQL AVG, MIN, MAX, LEAD, LAG Scalar SQL functions such as UPPER, LOWER, INITCAP and SUBSTR can be used in PL/SQL statements. However, the aggregate functions (AVG, MIN, MAX) and analytic functions (LEAD, LAG) are not permitted in PL/SQL statements. Of course, the aggregate and analytic functions can be used in SQL statements embedded in PL/SQL. Oracle also supplies error-related functions SQLERRM and SQLCODE for use in PL/SQL statements only. This slide shows an excerpt from a DECLARE block where we use these functions to initialize local variables. SQLERRM contains the text of the last error message; SQLCODE contains the Oracle error code. You will learn more about the use of these functions in the lesson on error handling later in this course.

51 Language Fundamentals Regular Expressions Like SQL, PL/SQL supports regular expressions 10g LINUX> declare 2 v1 v1 varchar2(20) := := 'abcdefg'; 3 begin begin 4 if if regexp_like(v1, '.*c*') then then null; null; end end if; if; 5 v1 v1 := := regexp_replace(v1, '.*c*', 'a'); 'a'); 6 dbms_output.put_line(v1); 7 end; end; 8 / aa aa PL/SQL procedure successfully completed. Like the Oracle 10g SQL compiler, the 10g PL/SQL compiler supports regular expressions. Oracle s implementation is IEEE POSIX and Unicode Consortium compliant. Oracle10g provides many new operators such as: * - Matches zero or more occurrences + - Matches one or more occurrences? - Matches zero or one occurrence ^ - Anchors to the beginning of the line $ - Anchors to the end of line Oracle 10g Release 2 adds support for Perl expressions, including, but not limited to: \d Match a digit character \D Match a non-digit character \w Match a word character \W Match a non-word character Notes for this slide continue on the next page