Chapter 5 Structured Query Language (SQL)

Chapter 5 Structured Query Language (SQL)

Database Systems: Design, Implementation, and Management

Peter Rob & Carlos Coronel

In this chapter, you will learn:In this chapter, you will learn:

The basic commands and functions of SQL How SQL is used for data manipulation (to add,

modify, delete, and retrieve data) How to use SQL to query a database to extract

useful information How SQL is used for data administration (to

create tables, indexes, and views) About more advanced SQL features such as

updatable views, stored procedures, and triggers

Introduction to SQLIntroduction to SQL

Ideal database language Create database and table structures Perform basic data management chores (add, delete,

and modify) Perform complex queries to transform data into useful

information

Introduction to SQLIntroduction to SQL SQL (Structured Query Language)

meets ideal database language requirements:

SQL coverage fits into two categories: Data definition

Data manipulation

SQL is relatively easy to learn.

ANSI prescribes a standard SQL.

SQL2 : SQL-92

SQL3 : SQL-98/99 support object-oriented data management

Data Definition CommandsData Definition Commands The Database Model

Simple Database -- PRODUCT and VENDOR tables Each product is supplied by only a single vendor. A vendor may supply many products.

Data Definition CommandsData Definition Commands The Tables and Their Components

The VENDOR table contains vendors who are not referenced in the PRODUCT table. PRODUCT is optional to VENDOR.

Some vendors have never supplied a product

( 0,N )

Data Definition CommandsData Definition Commands The Tables and Their Components

Existing V_CODE values in the PRODUCT table must have a match in the VENDOR table.

A few products are supplied factory-direct, a few are made in-house, and a few may have been bought in a special warehouse sale. That is, a product is not necessarily supplied by a vendor. VENDOR is optional to PRODUCT.

( 0,1 )

PRODUCT

VENDER

CH5_TEXT

Data Definition CommandsData Definition Commands

Create database structure Holds all tables and is a collection of physical files stored

on disk DBMS automatically creates tables to store metadata Database administrator creates structure or schema

Logical group of tables or logical database Groups tables by owner Enforces security

Data Definition CommandsData Definition Commands Creating the Database Structure

CREATE SCHEMA AUTHORIZATION <creator>;

Example:CREATE SCHEMA AUTHORIZATION JONES;

Schema : logical database structurea group of database objects- such as tables and indexes – that are related to each other.

CREATE DATABASE <database name>;

Example:CREATE DATABASE CH5;

A Data Dictionary for the CH5 Database

Table 5.1

Some Common SQL Data Types

Numeric NUMBER(L,D)INTEGERSMALLINTDECIMAL(L,D)

Character CHAR(L)VARCHAR(L)

Date DATE

Data Type Format


Creating Table Structures

CREATE TABLE <table name>(<attribute1 name and attribute1 characteristics, attribute2 name and attribute2 characteristics, attribute3 name and attribute3 characteristics, primary key designation, foreign key designation and foreign key requirements>);


CREATE TABLE VENDOR(V_CODE INTEGER NOT NULL UNIQUE, V_NAME VARCHAR(35) NOT NULL, V_CONTACT VARCHAR(15) NOT NULL, V_AREACODE CHAR(3) NOT NULL, V_PHONE CHAR(3) NOT NULL, V_STATE CHAR(2) NOT NULL, V_ORDER CHAR(1) NOT NULL, PRIMARY KEY (V_CODE));

CREATE TABLE PRODUCT( P_CODE VARCHAR(10) NOT NULL UNIQUE, P_DESCRIPT VARCHAR(35) NOT NULL, P_INDATE DATE NOT NULL, P_ONHAND SMALLINT NOT NULL, P_MIN SMALLINT NOT NULL, P_PRICE DECIMAL(8,2) NOT NULL, P_DISCOUNT DECIMAL(4,1) NOT NULL, V_CODE SMALLINT,

PRIMARY KEY (P_CODE), FOREIGN KEYFOREIGN KEY (V_CODE) REFERENCES REFERENCES VENDORVENDOR ON DELETE RESTRICT

ON UPDATE CASCADE);

ON DELETE RESTRICTcannot delete a vender as long as there is a product that references that vender

ON UPDATE CASCADEupdate V_CODE in VENDER → update V_CODE in PRODUCT

Data Definition CommandsData Definition Commands Adherence to entity integrity and

referential integrity rules is crucial

SQL Integrity Constraints Entity Integrity

PRIMARY KEY NOT NULL and UNIQUE

Referential Integrity FOREIGN KEY ON DELETE ON UPDATE

SQL Command Coverage

Table 5.3

Data Entry and SavingData Entry and Saving

Enters data into a table

Saves changes to disk

INSERT INTO <table name> VALUES (attribute 1 value, attribute 2 value, … etc.);

COMMIT <table names> ;

Basic Data ManagementBasic Data Management Data Entry

INSERT INTO <table name> VALUES (attribute 1 value, attribute 2 value, … etc.);

INSERT INTO VENDORVALUES(‘21225, ’Bryson, Inc.’, ’Smithson’, ’615’,’223-3234’, ’TN’, ’Y’);

INSERT INTO PRODUCTVALUES(‘11 QER/31’, ’Power painter, 15 psi., 3-nozzle’, ’07/02/1999’, 8.5, 109.99, 0.00, 25595);

Figure 5.3 A form-based Data View and Entry Screen

Basic Data ManagementBasic Data Management Saving the Table Contents

COMMIT <table names>;

COMMIT PRODUCT;

Any changes made to the table contentsare not physically saved on disk until

COMMIT close the database log out of SQL

Listing Table Contents and Other Commands

Listing Table Contents and Other Commands

Allows table contents to be listed

UPDATE command makes data entry corrections ROLLBACK command restores database back to

previous condition if COMMIT hasn’t been used DELETE command removes table row

SELECT <attribute names> FROM <table names>;

Basic Data ManagementBasic Data Management Listing the Table Contents

SELECT * FROM PRODUCT;

SELECT P_CODE, P_DESCRIPT, P_INDATE, P_ONHAND, P_MIN, P-PRICE, P_DISCOUNT, V_CODE FROM PRODUCT;

Figure 5.4 The Contents of the PRODUCT Table

Basic Data ManagementBasic Data Management Making a Correction

UPDATE PRODUCTSET P_INDATE = ‘12/11/96’WHERE P_CODE = ‘13-Q2/P2’;

UPDATE PRODUCTSET P_INDATE = ‘12/11/96’, P_PRICE = 15.99,

P_MIN = 10WHERE P_CODE = ‘13-Q2/P2’;

Basic Data ManagementBasic Data Management Restoring the Table Contents

ROLLBACK

If COMMIT not yet Does not require to specify the table name.

SQL assumes that the database currently in memoryis the one to be restored.

Update integrity in transaction management (Ch.9) COMMIT ROLLBACK

Basic Data ManagementBasic Data Management Deleting Table Rows

DELETE FROM PRODUCTWHERE P_CODE = ‘2238/QPD’;

DELETE FROM PRODUCTWHERE P_MIN = 5;

QueriesQueries Creating partial listings of table contents

SELECT <column(s)>FROM <table name>WHERE <conditions>;

Table 5.4 Mathematical Operators

QueriesQueries

Partial Listing of Table ContentsSELECT <column(s)>

FROM <table name>WHERE <conditions>;

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE V_CODE = 21344;

Figure 5.5

Figure 5.6

The Microsoft Access QBE and Its SQL

QBE (Query By Example)query generator

ExamplesExamples Mathematical operators

Mathematical operators on character attributes

Mathematical operators on dates

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE V_CODE <> 21344;

SELECT P_CODE,P_DESCRIPT,P_ONHAND,P_MIN,P_PRICEFROM PRODUCTWHERE P_CODE < ‘1558-QWI’;

SELECT P_DESCRIPT,P_ONHAND,P_MIN,P_PRICE,PINDATEFROM PRODUCTWHERE P_INDATE >= ‘01/20/2002’;

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE V_CODE <> 21344;

Figure 5.7

QueriesQueries

SELECT P_DESCRIPT, P_ONHAND, P_MIN, P_PRICEFROM PRODUCTWHERE P_PRICE <= 10;

Figure 5.8

QueriesQueries

Using Mathematical Operators on Character Attributes

SELECT P_DESCRIPT, P_ONHAND, P_MIN, P_PRICEFROM PRODUCTWHERE P_CODE < ‘1558-QWI’;

Figure 5.9

QueriesQueries

Using Mathematical Operators on Dates

SELECT P_DESCRIPT, P_ONHAND, P_MIN, P_PRICE, P_INDATE

FROM PRODUCTWHERE P_INDATE >= ‘08/15/1999’;

Figure 5.10

QueriesQueries

Computed Columns Computed Columns New columns can be created through valid

computations or formulas Formulas may contain mathematical operators May contain attributes of any tables specified in FROM

clause

Alias is alternate name given to table or column in SQL statement

SELECT P_DESCRIPT,P_ONHAND,P_PRICE, P_ONHAND*P_PRICE AS TOTVALUE FROM PRODUCT;

P_DESCRIPT P_ONHAND P_PRICE TOTVALUE

OperatorsOperators

Logical: AND, OR, NOT

Rules of precedence Conditions within parenthesis executed first Boolean algebra

Special BETWEEN - defines limits IS NULL - checks for nulls LIKE - checks for similar string IN - checks for value in a set EXISTS - opposite of IS NULL

SELECT *FROM PRODUCTWHERE V_CODE = 21344 OR V_CODE = 24288;

Logical Operators: AND, OR, and NOT

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE V_CODE=21344 OR V_CODE=24288;

Figure 5.13

QueriesQueries

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE P_PRICE<50 AND P_INDATE>‘07/15/1999’;

Figure 5.14

QueriesQueries

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODEFROM PRODUCTWHERE (P_PRICE<50 AND P_INDATE>07/15/1999’) OR V_CODE=24288;

Figure 5.15

QueriesQueries

QueriesQueries Special Operators

BETWEEN - used to define range limits.

IS NULL - used to check whether an attribute value is null

LIKE - used to check for similar character strings.

IN - used to check whether an attribute value matches a value contained within a (sub)set of listed values.

EXISTS - used to check whether an attribute has a value. - the opposite of IS NULL.

Special Operators

BETWEEN is used to define range limits.

SELECT * FROM PRODUCTWHERE P_PRICE BETWEEN 50.00 AND 100.00;

SELECT *FROM PRODUCTWHERE P_PRICE>50.00 AND P_PRICE<100.00;

QueriesQueries

Special OperatorsIS NULL is used to check whether an

attribute value is null.

SELECT P_CODE, P_DESCRIPT FROM PRODUCTWHERE P_MIN IS NULL;

SELECT P_CODE, P_DESCRIPT FROM PRODUCTWHERE P_INDATE IS NULL;

QueriesQueries

Special OperatorsLIKE is used to check for similar character strings.

SELECT * FROM VENDORWHERE V_CONTACT LIKE ‘Smith%’;

SELECT * FROM VENDORWHERE V_CONTACT LIKE ‘SMITH%’;

% : cn , c=any character, n 0≧

_ : c1

QueriesQueries

Special OperatorsIN is used to check whether an attribute value

matches a value contained within a (sub)set of listed values.

SELECT * FROM PRODUCTWHERE V_CODE IN (21344, 24288);

QueriesQueries

QueriesQueries EXISTS is used to check whether an

attribute has value.

DELETE FROM PRODUCTWHERE P_CODE EXISTS;

SELECT * FROM PRODUCTWHERE V_CODE EXISTS;

Advanced Data Management Commands


Changing Table Structures

ALTER TABLE <table name>MODIFY (<column name> <new column characteristics>);

ALTER TABLE <table name>ADD (<column name> <new column characteristics>);

Changing a Column’s Data Type

ALTER TABLE PRODUCTMODIFY (V_CODE CHAR(5));

Changing Attribute Characteristics

ALTER TABLE PRODUCTMODIFY (P_PRICE DECIMAL(9,2));

Adding a New Column to the Table

ALTER TABLE PRODUCTADD (P_SALECODE CHAR(1));



UPDATE PRODUCTSET P_SALECODE = ‘2’WHERE P_CODE = ‘1546-QQ2’;



UPDATE PRODUCTSET P_SALECODE = ‘1’WHERE P_CODE IN (‘2232/QWE’, ‘2232/QTY’);



UPDATE PRODUCTSET P_SALECODE = ‘2’WHERE P_INDATE < ‘07/10/1999’;

UPDATE PRODUCTSET P_SALECODE = ‘1’WHERE P_INDATE >= ‘08/15/1999’ AND P_INDATE < ‘08/20/1999’;



Selected PRODUCT Table Attributes: Multiple Update Effect



The Arithmetic Operators

Λ

Copying Parts of Tables Need not be identical:

Column names Number of columns

Column characteristics must match

CREATE TABLE PARTPART_CODE CHAR(8) NOT NULL UNIQUE,PART_DESCRIPT CHAR(35),PART_PRICE DECIMAL(8,2),PRIMARY KEY(PART_CODE));

INSERT INTO PART (PART_CODE,PART_DESCRIPT,PART_PRICE)SELECT P_CODE, P_DESCRIPT, P_PRICEFROM PRODUCT;



The Part Attributes Copied from the PRODUCT Table

Deleting a Table from the Database DROP TABLE <table name>;

DROP TABLE PART;



Primary and Foreign Key Designation For reestablish the integrity rules

Forgot to define Imported tables from a different database

ALTER TABLE PRODUCTADD PRIMARY KEY (P_CODE);

ALTER TABLE PRODUCTADD FOREIGN KEY (V_CODE) REFERENCES VENDOR;

ALTER TABLE PRODUCT ADD PRIMARY KEY (P_CODE) ADD FOREIGN KEY (V_CODE) REFERENCES VENDOR;



More Complex Queries and SQL Functions


Ordering a Listing

ORDER BY <attributes>

SELECT P_CODE, P_DESCRIPT, P_INDATE, P_PRICEFROM PRODUCTORDER BY P_PRICE;

Selected PRODUCT Table Attributes Ordered by(Ascending) P_PRICE

The Partial Listing of the EMPLOYEE Table

Cascading order sequenceSELECT EMP_LNAME,EMP_FNAME,EMP_INITIAL,EMP_AREACODE,EMP_PHONE

FROM EMPLOYEEORDER BY EMP_LNAME, EMP_FNAME, EMP_INITIAL;

Descending orderSELECT P_CODE, P_DESCRIPT, P_INDATE, P_PRICEFROM PRODUCTWHERE P_INDATE<‘08/20/1999’ AND P_PRICE<=50.00ORDER BY V_CODE, P_PRICE DESCDESC;

Listing Unique Values

SELECT DISTINCTDISTINCT V_CODEFROM PRODUCT;



FUNCTION OUTPUT

COUNT The number of rows containing the specified attribute.

MIN The minimum attribute value encountered.

MAX The maximum attribute value encountered.

AVG The arithmetic mean (average) for the specified attribute.

SUM The sum of all values for a selected attribute.

Some Basic SQL Aggregate Functions

Querying a Query: Nested Process

COUNT

SELECT COUNT(DISTINCTDISTINCT V_CODE)FROM PRODUCT;

6

COUNT Function Output Examples

MAX and MIN Function Output Examples

MAX

SELECT P_CODE, P_DESCRIPT, P_PRICEFROM PRODUCTWHERE P_PRICE = (SELECT MAX(P_PRICE) FROM PRODUCT);

SUM

SELECT SUM(P_ONHAND*P_PRICE)FROM PRODUCT;

AVG

SELECT P_DESCRIPT, P_ONHAND, P_PRICE, V_CODEFROM PRODUCTWHERE P_PRICE > (SELECT AVG(P_PRICE) FROM PRODUCT)ORDER BY P_PRICE DESC;



AVG Function Output Examples

• Determine whether goods that have been in inventory for a certain length of time should be placed on special sale.

Grouping Data

GROUP BY

SELECT P_SALECODE, MIN(P_PRICE)FROM PRODUCT_2GROUP BY P_SALECODE;

GROUP BY clauseGROUP BY clause The GROUP BY clause is valid only

when used in conjunction with one of the SQL arithmetic functions:COUNT, MIN, MAX, AVG, SUM

SELECT V_CODE, COUNT(DISTINCT(P_CODE))

FROM PRODUCT_2GROUP BY V_CODE;

Otherwise, you will generate a “not a GROUP BY expression” error.

SELECT V_CODE, P_CODE, P_DESCRIPT, P_PRICE

FROM PRODUCT_2GROUP BY V_CODE;

Improper Use of the GROUP BY Clause

ERRORERROR

GROUP BY’s HAVING clauseGROUP BY’s HAVING clause WHERE ( SELECT )

Applies to columns and expressions for individual rows HAVING ( GROUP BY )

Applies to the output of a GROUP BY command

SELECT V_CODE,COUNT(DISTINCT(P_CODE)),AVG(P_PRICE) FROM PRODUCT_2GROUP BY V_CODE;

SELECT V_CODE,COUNT(DISTINCT(P_CODE)),AVG(P_PRICE) FROM PRODUCT_2GROUP BY V_CODE HAVING AVG(P_PRICE)<10;

An Application of the HAVING Clause

Virtual Tables: Creating a View Logical table exists only in memory Can be treated as though it were a real table

CREATE VIEW PRODUCT_3 AS

SELECT P_DESCROPT, P_ONHAND, P_PRICE

FROM PRODUCTWHERE P_PRICE > 50.0;



Creating a ViewCreating a View

SQL Indexes Improve the efficiency of data search Created to meet particular search criteria

CREATE INDEX P_CODEX ON PRODUCT(P_CODE);

When the index field is a primary key whose values must not be duplicated

CREATE UNIQUE INDEX P_CODEXON PRODUCT(P_CODE);



Joining Database Tables

SELECT PRODUCT.P_DESCRIPT,PRODUCT.P_PRICE, VENDOR.V_NAME, VENDOR.V_CONTACT, VENDOR.V_AREACODE, VENDOR.V_PHONEFROM PRODUCT, VENDORWHERE PRODUCT.V_CODE=VENDOR.V_CODE;



The Results of a JOIN

SELECT P_DESCRIPT, P_PRICE, V_NAME, V_CONTACT, V_AREACODE, V_PHONEFROM PRODUCT, VENDORWHERE PRODUCT.V_CODE=VENDOR.V_CODE AND P_INDATE > ‘08/15/1999’;



Procedural languageProcedural language

A term used in contrast to declarative language to describe a language where the programmer specifies an explicit sequences of steps to follow to produce a result.

Common procedural languages include Basic, Pascal, C.

Declarative languages describe relationships between variables in terms of functions or inference rules and the language executor (interpreter or compiler) applies some fixed algorithm to these relations to produce a result.

The most common examples of declarative languages are logic programming languages such as Prolog and functional languages like Haskell.

Procedural SQLProcedural SQL

Shortcomings of SQL SQL doesn’t support execution of a stored set of procedures

based on some logical condition.IF-THEN-ELSE

SQL fails to support the looping operations.DO-WHILE

Solutions Embedded SQL

SQL statements can be inserted within the procedural programming language

Shared Code Critical code is isolated and shared by all application programs. This approach allows better maintenance.

Procedural SQL(PL/SQL)

Procedural SQLProcedural SQL Procedural SQL

Procedural SQL allows the use of procedural code and SQL statements that are stored within the database.

The procedural code is executed by the DBMS when it is invoked by the end user.

End users can use PL/SQL to create: Triggers Stored procedures PL/SQL functions

Procedural SQLProcedural SQL Triggers

A trigger is procedural SQL code that is automatically invoked by the RDBMS upon the occurrence of a data manipulation event.

A trigger is always invoked before or after a data row is selected, inserted, or updated.

A trigger is always associated with a database table.

Each database table may have one or more triggers.

A trigger is executed as part of the transaction that triggered it.

Procedural SQLProcedural SQL Role of triggers

Triggers can be used to enforce constraints that cannot be enforced at the design and implementation levels.

Triggers add functionality by automating critical actions and providing appropriate warnings and suggestions for remedial action.

Triggers can be used to update table values, insert records in tables, and call other stored procedures.

The Revised PRODUCT Table

If P_ONHAND(庫存 ) <= P_MIN(安全存量 )set P_REORDER = “Yes”

The PRODUCT List Output in the Oracle RDBMS

in Oracle :P_REORDER = 1/0 for Yes/No

Procedural SQLProcedural SQL Syntax to create a trigger in ORACLE

CREATE OR REPLACE TRIGGER <trigger_name>[BEFORE/AFTER][DELETE/INSERT/UPDATE OF <column_name>] ON <table_name>[FOR EACH ROW]BEGIN

PL/SQL instructions;……………

END;

Procedural SQLProcedural SQL Creation of the Oracle Trigger for the PRODUCT

Table

CREATE OR REPLACE TRIGGER TRG_PRODUCT_REORDERAFTER INSERT OR UPDATE OF P_ONHAND ON PRODUCTBEGIN

UPDATE PRODUCT

SET P_REORDER = 1

WHERE P_ONHAND <= P_MIN;END;

Creation of the Oracle Trigger for the PRODUCT Table

The PRODUCT Table’s P_REORDER Field isUpdated by the Trigger

UPDATE PRODUCT

SET P_ONHAND = 4 WHERE P_CODE = ’11QER/31’;

The P_REORDER Value Mismatch

UPDATE PRODUCT

SET P_MIN = 7 WHERE P_CODE = ’2232/QWE’;

The Second Version of the PRODUCT_REORDER Trigger

CREATE OR REPLACE TRIGGER TRG_PRODUCT_REORDER

AFTER INSERT OR UPDATE OF P_ONHAND, P_MIN

ON PRODUCTBEGIN

UPDATE PRODUCT

SET P_REORDER = 1

WHILE P_ONHAND <= P_MIN;END;

The Second Version of the PRODUCT_REORDER Trigger

UPDATE PRODUCT

SET P_MIN = 10 WHERE P_CODE = ’23114-AA’;

The P_REORDER Flag Has Not Been Properly Set AfterIncreasing the P_ONHAND Value

UPDATE PRODUCT

SET P_ONHAND = P_ONHAND + P_MIN WHERE P_CODE = ’11QER/31’;

4 25

Never reset it to 0!

The Third Version of the PRODUCT_REORDER Trigger

CREATE OR REPLACE TRIGGER TRG_PRODUCT_REORDERBEFORE INSERT OR UPDATE OF P_ONHAND, P_MIN

ON PRODUCTBEGIN

IF :NEW.P_ONHAND <= NEW.P_MIN THEN

:NEW.P_REORDER = 1;

ELSE

:NEW.P_REORDER = 0;

END IF;END;

The Third Version of the Product Reorder Trigger

After creating the new trigger, we can execute an UPDATE statement to fire it.

UPDATE PRODUCT

SET P_ONHAND = P_ONHAND

Execution of the Third Trigger Version

Procedural SQLProcedural SQL Stored Procedures

A stored procedure is a named collection of procedural and SQL statements.

Stored procedures are stored in the database and invoked by name.

Stored procedures are executed as a unit.

Procedural SQLProcedural SQL Syntax to create a stored procedure

CREATE OR REPLACE PROCEDURE procedure_name (argument IN/OUT data-type, etc) IS/AS BEGIN

DECLARE variable name and data typePL/SQL or SQL statements;

END;

Syntax to invoke a stored procedure

EXEC store_procedure_name(parameter, parameter, …)

Procedural SQLProcedural SQL Stored Procedures

DECLARE is used to specify the variables used within the procedure.

Argument specifies the parameters that are passed to the stored procedure.

IN / OUT indicates whether the parameter is for INPUT or OUTPUT or both.

Data-type is one of the procedural SQL data types used in the RDBMS.

Creating and Invoking A Simple Stored Procedure

The PROD_SALE Stored Procedure

CREATE OR REPLACE PROCEDURE PROD-SALE (CODE IN VARCHAR2, QTYSOLD IN NUMBER)

AS BEGINUPDATE PRODUCT

SET P_ONHAND = P_ONHAND - QTYSOLD

WHERE P_CODE = CODE;

END;

Creation of the PROD_SALE Stored Procedure

Executing the PROD_SALE Stored Procedure

Procedural SQLProcedural SQL PL/SQL Stored Functions

A stored function is a named group of procedural and SQL statements that returns a value.

Syntax to create a function:

CREATE FUNCTION function_name (argument IN data-type, etc)RETURN data-typeAS BEGIN

PL/SQL statements;RETURN (value); ……

END;

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Chapter 5 Structured Query Language (SQL)

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