database programs cs 260 database systems. overview introduction anonymous blocks oracle’s...

DATABASE PROGRAMSCS 260

Database Systems

Overview

Introduction Anonymous blocks

Oracle’s PL/SQL language basics Conditions and loops Cursors and SQL commands in PL/SQL Exception handling

Stored programs Procedures Functions Packages Triggers

Introduction

A database program is used to automate data processing

It is written using a procedural language extension that is specific to the DBMS Oracle: PL/SQL

“Procedural Language/Structured Query Language” MySQL: MySQL Microsoft SQL Server: T-SQL

“Transact-SQL” IBM DB2: SQL PL

DB2 also runs PL/SQL

Introduction

Why do we need database programs? Addresses the limitations of SQL commands

SQL has no conditional statements or looping mechanisms Database programs are helpful for importing and exporting

data You can only go so far with nested queries An SQL query returns a tabular result set, stored programs

can manipulate this format Why not just put stored program logic in an

application? “Stored programs” are accessible to any application using

the db Database programs interface directly with the database

More efficient in terms of both speed and lines of code DBMS can manage security issues

Introduction

Why might we want to avoid database programs? They increase the DBMS server’s load Writing the program logic in an external

application may allow for more flexibility Database programs may be more difficult

to debug

Introduction

PL/SQL Example This stored program identifies the number

of days until Christmas

CREATE OR REPLACE FUNCTION shopping_days_xmas(current_date IN DATE) RETURN NUMBER IS shopping_days NUMBER;BEGIN shopping_days := TO_DATE('25-DEC-2015', 'DD-MON-YYYY') - current_date; RETURN shopping_days;END;

Introduction

Types of PL/SQL programs Anonymous blocks

Not persistent (not stored in the database) Cannot be called by other programs No parameters/arguments

Stored programs Stored as database objects

Procedures Functions Packages Triggers

Can be called by other programs Allow parameters/arguments

Overview




PL/SQL Language Basics

Basic program structure Statements may span multiple lines and

end with a semicolon Text is not case sensitive Basic anonymous block program syntax

/* block comment */DECLARE

<variable declarations>;BEGIN

<program statements>; --line commentEXCEPTION

<error handling statements>;END;


Variables Names must follow the Oracle object

naming standard Names should be descriptive Naming conventions

Use lowercase letters with words separated by underscores

Example: current_student_id


PL/SQL is a strongly-typed language All variables must be declared with a type

prior to use Declaration syntax

Declaration example

Initialization example

<variable_name> <data_type>;

current_student_id NUMBER(6);

current_student_id NUMBER(6) := 1;


Common data types SQL data types

VARCHAR2, CHAR NUMBER DATE

Non-SQL data types Integers

BINARY_INTEGER, INTEGER, INT, SMALLINT, … Real numbers

DEC, DECIMAL, DOUBLE, PRECISION, NUMBERIC, REAL, … BOOLEAN

Composite data types RECORD, TABLE, VARRAY


Reference data types %TYPE

Assumes the data type of a database field Variable declaration example

%ROWTYPE Creates a RECORD data type that holds the data

types present in the returned SQL query RECORDS are ordered collections of specific data types %ROWTYPE creates a RECORD according to the types in

a result Syntax

current_cust_name candy_customer.cust_name%TYPE;

<variable_name> <cursor_name>%ROWTYPE;


Basic OperatorsExponentiation **

Multiplication *

Division /

Addition/Subtraction +/-

Assignment :=

Comparison =

Concatenation ||


Displaying PL/SQL output using Oracle SQL Developer Enable and/or increase memory buffer

Necessary to see PL/SQL output on the console Output data to the console

SET SERVEROUTPUT ON SIZE 4000;

DBMS_OUTPUT.PUT_LINE(‘<output>’);

DBMS_OUTPUT.PUT_LINE(‘Output: ’ || <variable or function>);


Anonymous block example This program prints the current date to the

console in the format “Today is <date>”

SET SERVEROUTPUT ON SIZE 4000;

DECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE ('Today is ' || todays_date);END;


Anonymous block example output

Overview




Conditions and Loops

Conditional statements Syntax

0 or more “ELSIF” statements Optional “ELSE” statement

IF <condition> THEN <statements>;ELSIF <condition> THEN <statements>;ELSE <statements>;END IF;


Conditional statement example This program extends the functionality of the

previous program by also indicating whether Christmas is coming or has passed

DECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE ('Today is ' || todays_date); IF todays_date > to_date('25-JUN', 'DD-MON') THEN DBMS_OUTPUT.PUT_LINE ('Christmas is coming!'); ELSE DBMS_OUTPUT.PUT_LINE ('Christmas has passed.'); END IF;END;


EXIT WHEN loop (equivalent to Java do-while loop) Syntax

Example

LOOP <statements>;EXIT WHEN <condition>;END LOOP;

DECLARE i NUMBER;BEGIN i := 0; LOOP i := i+1; DBMS_OUTPUT.PUT_LINE ('i is ' || i); EXIT WHEN i = 10; END LOOP;END;


WHILE loop (equivalent do Java while loop) Syntax

Example

WHILE <condition>LOOP <statements>;END LOOP;

DECLARE i NUMBER;BEGIN i := 0; WHILE i < 10 LOOP i := i+1; DBMS_OUTPUT.PUT_LINE ('i is ' || i); END LOOP;END;


FOR loop (equivalent do Java for loop) Syntax

Example

FOR <counter> IN <start_value> .. <end_value>LOOP <statements>;END LOOP;

BEGIN FOR i IN 1 .. 10 LOOP DBMS_OUTPUT.PUT_LINE ('i is ' || i); END LOOP;END;

You cannot manually update the for loop counter within the loop

Overview




Cursors and SQL in PL/SQL

Using SQL within a PL/SQL ProgramSQL Command Category

Purpose Examples Can be used in PL/SQL

Data Definition Language (DDL)

Change database structure

CREATE, ALTER, GRANT, REVOKE

No

Data Manipulation Language (DML)

View or change data

SELECT, INSERT, UPDATE, DELETE

Yes

Transaction Control

Create logical transactions

COMMIT, ROLLBACK

Yes

--create table to store all dates in 2015CREATE TABLE dates_2015 ( date_value DATE );--program to insert datesSET SERVEROUTPUT ON SIZE 4000;DECLARE first_date DATE := '01-JAN-2015'; counter INT := 0;BEGIN WHILE counter < 365 LOOP INSERT INTO dates_2015 VALUES (first_date + counter); DBMS_OUTPUT.PUT_LINE(first_date + counter); counter := counter + 1; END LOOP; COMMIT;END;


Example looping program

SQL can exist in the same script as PL/SQL

DML and Transaction control can exist within PL/SQL


Using SELECT commands in PL/SQL Create a “cursor” to allow the PL/SQL

program to reference the retrieved values Cursor: “CURrent Set Of Records” Pointer to a memory location on the database

server Cursor types

Implicit Explicit


Implicit cursors Can be used for SELECT queries that return

one (and only one) record The query must return a record

Can be used to assign the column values returned by a SELECT statement into one or more variables

The variables need to be declared, but the cursor itself does not


Implicit cursors Syntax

Usage The number of variables in the INTO clause must

match the number of fields in the SELECT clause The corresponding field/variable data types must

be compatible %TYPE may be useful here

SELECT <field1>, <field2>, …INTO <variable1>, <variable2>, …FROM <table>WHERE <search_condition_that_will_return_a_single_record>;


Implicit cursor example This program places the cust_name and

cust_addr of the candy_customer with a cust_id = 1 into the program’s curr_cust_name and curr_cust_add variablesDECLARE curr_cust_name candy_customer.cust_name%TYPE; curr_cust_add candy_customer.cust_addr%TYPE;BEGIN SELECT cust_name, cust_addr INTO curr_cust_name, curr_cust_add FROM candy_customer WHERE cust_id = 1; DBMS_OUTPUT.PUT_LINE(curr_cust_name); DBMS_OUTPUT.PUT_LINE(curr_cust_add);END;


Explicit cursors Can be used for SELECT queries that return zero,

one, or multiple records Can be used to assign the column values returned

by a SELECT statement into one or more variables Both the variables and the cursor need to be

declared Explicit cursors are processed sequentially using a

loop The loop typically iterates through each record in the

result set The cursor points to the current record


Using an explicit cursor1. Declare the cursor in the DECLARE section2. Open the cursor in the program3. Fetch the cursor result into PL/SQL

program variables4. Close the cursor


Explicit cursor example This program loops through all candy_customer

cust_id and cust_name values obtained using a cursor and prints them to the console

DECLARE CURSOR customer_cursor IS SELECT cust_id, cust_name FROM candy_customer; curr_id candy_customer.cust_id%TYPE; curr_name candy_customer.cust_name%TYPE;BEGIN OPEN customer_cursor; LOOP FETCH customer_cursor INTO curr_id, curr_name; EXIT WHEN customer_cursor%NOTFOUND; DBMS_OUTPUT.PUT_LINE(curr_id || ' ' || curr_name); END LOOP; CLOSE customer_cursor;END;


Alternate version of explicit cursor example Uses a single variable of %ROWTYPE data type

instead of separate variables for each fieldDECLARE CURSOR customer_cursor IS SELECT cust_id, cust_name FROM candy_customer; customer_row customer_cursor%ROWTYPE;BEGIN OPEN customer_cursor; LOOP FETCH customer_cursor INTO customer_row; EXIT WHEN customer_cursor%NOTFOUND; DBMS_OUTPUT.PUT_LINE(customer_row.cust_id || ' ' ||

customer_row.cust_name); END LOOP; CLOSE customer_cursor;END;


Processing an explicit cursor Using a cursor FOR loop

Special syntax just for explicit cursors Automatically opens, processes, and closes the

cursor Automatically terminates after all cursor

records are processed Allows for much less code


Previous example using a cursor FOR loop

DECLARE CURSOR customer_cursor IS SELECT cust_id, cust_name FROM candy_customer; customer_row customer_cursor%ROWTYPE;BEGIN FOR customer_row IN customer_cursor LOOP --process each row DBMS_OUTPUT.PUT_LINE(customer_row.cust_id || ' ' ||

customer_row.cust_name); END LOOP;END;

Overview




Exception Handling

Exception handling An exception may occur due to a runtime

error or an event that violates a business rule

If the exception isn’t handled, the program will terminate and a default error message will be displayed

If the exception is handled, the program can continue executing and/or a custom error message can be displayed

Exception Handling

Program flow with and without exception handling

Program Body

System displays a default error messageand program terminates

error

Program Body

Exception handlers

error

System can display acustom error message

without with

Program optionally executes

additional statements

Exception Handling

Exception types Predefined (named)

Most common system errors have corresponding named exceptions

User-defined (named) Handle application specific errors (business

rules) Undefined (unnamed)

Used for less common system errors Built-in exception handler is associated with the

ORA error code number

Exception Handling

Syntax for handling predefined named exceptions

DECLARE <statements>;BEGIN <statements>;EXCEPTION WHEN <exception_name> THEN <statements>;END;

Exception Handling

Common PL/SQL named exceptions

Exception Handling

Handling a predefined named exception example This program retrieves and prints a cust_name to the

console, but inappropriately retrieves more than one record using an implicit cursor

The “TOO_MANY_ROWS” named exception is handled

DECLARE curr_cust_id candy_customer.cust_id%TYPE; curr_cust_name candy_customer.cust_name%TYPE;BEGIN SELECT cust_name INTO curr_cust_name FROM candy_customer; DBMS_OUTPUT.PUT_LINE(curr_cust_name);EXCEPTION WHEN TOO_MANY_ROWS THEN DBMS_OUTPUT.PUT_LINE('Change your query so it' || ' retrieves only one record');END;

Exception Handling

Syntax for creating, raising, and handling user-defined exceptions Declare exception as a variable in the DECLARE

section Raise the exception in the program (in the BEGIN

section) when appropriate using the RAISE command

DECLARE <exception_name> EXCEPTION;BEGIN RAISE <exception_name>;EXCEPTION WHEN <exception_name> THEN <statements>;END;

Exception Handling

Creating, raising, and handling a user-defined exception exampleDECLARE curr_purch_id candy_purchase.purch_id%TYPE := 1; curr_purch_date candy_purchase.purch_date%TYPE; new_delivery_date DATE := '05-SEP-07'; e_invalid_date EXCEPTION; BEGIN SELECT purch_date INTO curr_purch_date FROM candy_purchase WHERE purch_id = curr_purch_id; IF curr_purch_date <= new_delivery_date THEN UPDATE candy_purchase SET delivery_date = new_delivery_date WHERE purch_id = curr_purch_id; ELSE RAISE e_invalid_date; END IF; COMMIT; EXCEPTION WHEN e_invalid_date THEN DBMS_OUTPUT.PUT_LINE('Delivery date cannot be before purchase date, please change it'); END;

Exception Handling

Syntax for handling unnamed exceptions Unnamed exceptions can be identified by their SQL

codes Named exceptions must be handled first The SQLERRM function returns a message describing the

error Potentially useful when handling an unnamed exception

DECLARE <statements>;BEGIN <statements>;EXCEPTION -- handle named exceptions first WHEN OTHERS THEN IF SQLCODE = <sqlcode> THEN <statements>;END;

Exception Handling

Handling an unnamed exception exampleDECLARE

new_candy_product_id candy_product.prod_id%TYPE := 100;BEGIN --update an FK value using a non-existent value UPDATE candy_purchase SET prod_id = new_candy_product_id WHERE purch_id = 1;EXCEPTION -- ...named exception handlers WHEN OTHERS THEN IF SQLCODE = -2291 THEN DBMS_OUTPUT.PUT_LINE('Product ID ' || new_candy_product_id || ' does not exist.'); DBMS_OUTPUT.PUT_LINE('Message: ' || SQLERRM ); END IF;END;

SQL code list: http://psoug.org/oraerror.htm

Exception Handling

Exception scope and propagation Exception handlers only handle exceptions

thrown in their BEGIN block Nested blocks can be created so that outer

block execution isn’t impacted by inner block exceptions After an exception is raised and handled, all

uncommitted transactions are rolled back Execution resumes in the outer block

Exception Handling

Nested block syntax

DECLARE <outer block declarations>;BEGIN <outer block statements>; DECLARE

<inner block declarations>; BEGIN

<inner block statements>; EXCEPTION <inner block exception handlers>; END; <more outer block statements>;EXCEPTION <outer block exception handlers>;END;

Exception Handling

Suppose the cust_type of “W” was assumed to be removed and updated for all customers in our candy database

Write an anonymous block that does the following: Print the name and cust_type of each

customer If the cust_type is anything other than ‘P’ or

‘R’, raise a custom “invalid_cust_type” exception

If this exception is raised, the program should print the name and invalid cust_type and continue processing

Overview




Stored PL/SQL Programs

Can be executed by other programs and users Can accept input parameters They’re database objects

Permissions must be granted as needed Names must be unique in their schemas Follow object naming standards and conventions

Stored in a compiled form Types of stored PL/SQL programs

Procedures Functions Packages Triggers

Stored PL/SQL Programs

Parameter modes IN

Default parameter mode (used if no mode is specified) Used to pass values into the program Similar to Java’s pass-by-value argument passing scheme

OUT Used to pass values out of the program

Useful for procedures as they cannot “return” values Acts like an uninitialized variable

It should be assigned a value

IN OUT Used to both pass values into and out of the program Similar to C++’s pass-by-reference argument passing

scheme

Overview




Stored Procedures

Stored procedures allow parameters, can call other programs, but cannot return a value SyntaxCREATE OR REPLACE PROCEDURE <procedure_name>

(<param1> <mode> <datatype>, <param2> <mode> <datatype>, …) IS <variable declarations>;BEGIN <program statements>;EXCEPTION <exception handlers>;END;/

“AS” can be used in place of “IS”

Header

Body

Stored Procedures

Stored procedure exampleCREATE OR REPLACE PROCEDURE update_delivery_date (curr_purch_id IN candy_purchase.purch_id%TYPE, new_delivery_date IN DATE)IS -- local variable curr_purch_date candy_purchase.purch_date%TYPE; BEGIN -- implicit cursor (only one row returned) SELECT purch_date INTO curr_purch_date FROM candy_purchase WHERE purch_id = curr_purch_id; IF curr_purch_date <= new_delivery_date THEN UPDATE candy_purchase SET delivery_date = new_delivery_date WHERE purch_id = curr_purch_id; DBMS_OUTPUT.PUT_LINE('Delivery date updated'); END IF; COMMIT; END;/

Stored Procedures

Calling a stored procedure Stored procedures can be called from an

SQL script or a PL/SQL program SQL script syntax

Example

PL/SQL example (anonymous block)

EXECUTE <procedure_name>(<comma separated list of arguments);

EXECUTE update_delivery_date (1, SYSDATE);

BEGIN update_delivery_date (1, SYSDATE);END;

Overview




Stored Functions

Stored functions are similar to stored procedures, but they return a single value SyntaxCREATE OR REPLACE FUNCTION <function_name>

(<param1> <mode> <datatype>, <param2> <mode> <datatype>, …)RETURN <datatype> IS <variable declarations>;BEGIN <program statements>; RETURN <value>; EXCEPTION <exception handlers>; RETURN <value>;END;/

“AS” can be used in place of “IS”

Header

Body

Exception handlers should return a value

Stored Functions

Stored function example

Example call from an SQL script

CREATE OR REPLACE FUNCTION calc_diff (date1 IN DATE, date2 IN DATE)RETURN NUMBER IS days_passed NUMBER;BEGIN days_passed := date1 - date2; RETURN days_passed;END;/

SET SERVEROUTPUT ON SIZE 4000;EXEC DBMS_OUTPUT.PUT_LINE(calc_diff('25-DEC-2014', SYSDATE));

Stored Functions

Calling a stored function Stored functions can also be called from

within an SQL statement or a PL/SQL program

Syntax Can be called anywhere a value of the return

type is allowed ExamplesSELECT purch_id, calc_diff(delivery_date, purch_date)FROM candy_purchase;

SELECT purch_idFROM candy_purchaseWHERE calc_diff(delivery_date, purch_date) > 0;

Overview




Packages

A package is an object that groups related PL/SQL objects, such as variables, cursors, procedures, and functions

It consists of a specification and a body Specification

Declares a public interface Body

Contains a private implementation Clients can reference and call objects declared in

the specification, but not those declared in the body Similar to header and source files in C++

Packages

Benefits of packages Encapsulation of related objects Information hiding

Clients cannot see the implementation details in the body

If a procedure is declared in the body (and not the specification), it can be called only from within the package body

Better performance Package specifications and bodies are compiled

separately If changes to the body are needed, only the

package body needs to be recompiled instead of all clients that call objects in the package body

Packages

Package specification syntax

CREATE OR REPLACE PACKAGE <package_name>IS --public variables and cursors <variable_name> <datatype>; CURSOR <cursor_name> IS <SQL_statement>; … --procedures & functions PROCEDURE <procedure_name> (<parameter_list>); FUNCTION <function_name> (<parameter_list>) RETURN <data type>; …END;/

Packages

Package specification example

The public variables “max_pounds” and “curr_purch_id” can be used within the “update_pounds” and “update_delivery_date” implementations They can also be used anywhere access to the package is

allowed

CREATE OR REPLACE PACKAGE purchase_package IS --public variable declarations max_pounds NUMBER := 100; curr_purch_id candy_purchase.purch_id%TYPE;

--procedure declarations PROCEDURE update_pounds (new_pounds IN NUMBER); PROCEDURE update_delivery_date (new_delivery_date IN DATE);END;/

Packages

Example package bodyCREATE OR REPLACE PACKAGE BODY purchase_package IS PROCEDURE update_delivery_date (new_delivery_date DATE) IS curr_purch_date candy_purchase.purch_date%TYPE; BEGIN SELECT purch_date INTO curr_purch_date FROM candy_purchase WHERE purch_id = curr_purch_id; IF curr_purch_date <= new_delivery_date THEN UPDATE candy_purchase SET delivery_date = new_delivery_date WHERE purch_id = curr_purch_id; END IF; COMMIT; END; PROCEDURE update_pounds (new_pounds NUMBER) IS BEGIN IF new_pounds <= max_pounds THEN UPDATE candy_purchase SET pounds = new_pounds WHERE purch_id = curr_purch_id; END IF; COMMIT; END;END;/

Procedure 1

Procedure 2

Packages

When referencing or calling an object in a package, it is prefaced with its package name Syntax

Example (called from an SQL script)

The EXECUTE command isn’t used when referencing or calling package objects from within a PL/SQL block

For example, dbms_output.put_line(‘…’); is an example of calling a procedure inside the dbms_output package

<package_name>.<reference/call>;

EXECUTE purchase_package.curr_purch_id := 1;EXECUTE purchase_package.update_pounds(3.7);

Packages

When creating a package body, use the SHOW ERRORS command to print errors to the console

Oracle built-in packages Provide support for basic database functionality Owned by the SYS database schema Visible using the “Connections” pane in Oracle

SQL Developer Expand your schema > Other Users > SYS >

Packages

<package body>/SHOW ERRORS;

Overview




Triggers

Database triggers are programs that are attached to specific database tables

They may be executed in response to the following table operations: INSERT UPDATE DELETE

Triggers

Why are triggers useful? Force related operations to always happen

Update a “quantity on hand” field whenever an item is sold

Update a “current enrollment total” field whenever a student enrolls in a course section

Create an audit trail Record the username and IP address of every

user who changes a table For example, record who changed a student grade,

when they changed it, what they changed it from, and what they changed it to

Triggers

When defining a trigger, the following must be specified: Operation that causes the trigger to fire

INSERT, UPDATE, or DELETE Timing

BEFORE or AFTER the operation occurs Level

STATEMENT or ROW

Triggers

Trigger timing BEFORE

The trigger fires before the statement executes For example, for an audit trail, record the old

grade value before it is updated Though it’s still possible to accomplish this using

AFTER

AFTER The trigger fires after the statement executes For example, update the “quantity on hand”

after an item is sold

Triggers

Trigger levels ROW

The trigger fires once for each row that is affected For example, update a corresponding “quantity

on hand” value for each item that was sold STATEMENT

The trigger fires once regardless of how many rows are updated

For example, for an audit trail, you just want to record that someone updated a table, but you don’t care how many rows were updated

Triggers

Restrictions Triggers cannot have any parameters Triggers can only be created on tables that

you own Triggers cannot execute a COMMIT

command This is handled by the transaction firing the

trigger Triggers can be enabled or disabled

ALTER TRIGGER <trigger_name> <ENABLE or DISABLE>;

Triggers

Creation syntax

Choose one of “BEFORE” or “AFTER” Choose one or more of “INSERT”, “UPDATE”, and “DELETE”,

separated by “OR” “FOR EACH ROW” is optional

The trigger has statement level if omitted “WHEN (<condition>)” is optionally used only at the ROW

level Causes trigger to fire only when the row satisfied the condition

CREATE OR REPLACE TRIGGER <trigger_name> <BEFORE or AFTER> <INSERT or UPDATE or DELETE> ON <table_name> [FOR EACH ROW] [WHEN (<condition>)]BEGIN <trigger_body>;END;/

Triggers

Statement level exampleCREATE TABLE purchase_audit( date_changed DATE, user_changing VARCHAR2(30));

CREATE OR REPLACE TRIGGER purchase_audit AFTER INSERT OR UPDATE OR DELETE ON candy_purchaseBEGIN INSERT INTO purchase_audit VALUES (SYSDATE, USER);END;/SHOW ERRORS;

UPDATE candy_purchase SET pounds = 4.5 WHERE purch_id = 1 AND prod_id = 1;

SELECT * FROM purchase_audit;

USER returns the database user executing the statement

Triggers

Row level exampleCREATE TABLE purchase_audit_row(purch_id NUMBER(9), old_pounds NUMBER, new_pounds NUMBER, change_date DATE, change_user VARCHAR2(30));

CREATE OR REPLACE TRIGGER purchase_audit_row BEFORE UPDATE ON candy_purchase FOR EACH ROW BEGIN INSERT INTO purchase_audit_row VALUES( :OLD.purch_id, :OLD.pounds, :NEW.pounds, SYSDATE, USER);END;/SHOW ERRORS;

SELECT * FROM purchase_audit_row;UPDATE candy_purchase SET pounds = 15 WHERE purch_id = 5;SELECT * FROM purchase_audit_row;

:OLD.<field_name> references a field’s old value:NEW.<field_name> references a field’s new value

Triggers

Trigger design (from Oracle) Triggers should not duplicate features already

built into the database E.g. Checking constraints

If size is much more than 60 lines, place logic in a stored procedure and call from the trigger

Triggers should not be recursive For example, a trigger should not update a table if it’s

been designed to fire after updates are made to that table

Causes out of memory errors Because of their potentially frequent use, they

should be designed and implemented carefully

PL/SQL Programs in Scripts

Using PL/SQL programs in scripts PL/SQL programs in a script must be

followed by a single forward slashCREATE OR REPLACE PACKAGE show_message IS PROCEDURE hello_world;END;/CREATE OR REPLACE PACKAGE BODY show_message IS PROCEDURE hello_world IS BEGIN DBMS_OUTPUT.PUT_LINE('Hello World'); END;END;/SET SERVEROUTPUT ON SIZE 4000;BEGIN show_message.hello_world();END;/

database programs cs 260 database systems. overview introduction anonymous blocks oracle’s...

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