IT 20303 The Relational DBMS Section 07. Relational Database Theory Using a Relational DBMS.

IT 20303

• The Relational DBMS

• Section 07

Relational Database Theory

• Using a Relational DBMS

• Data Types– Depends on the conventions used by a

particular database– ORACLE uses:

• NUMBER• CHAR - Characters

• VARCHAR2 - Characters• DATE/TIME• LOB


• NUMBERNUMBER– Numerical dataNumerical data– Guaranteed to 38 digits accuracyGuaranteed to 38 digits accuracy– NUMBER(10) – 10 digits allowedNUMBER(10) – 10 digits allowed

• CHARCHAR– Character dataCharacter data– Fixed-Length up to 2,000 bytesFixed-Length up to 2,000 bytes– Good for 2 or 3 charactersGood for 2 or 3 characters– Y/N, T/F, USA/CANY/N, T/F, USA/CAN– CHAR(2) – 2 characters allowedCHAR(2) – 2 characters allowed


• VARCHAR2– Character data– Variable-Length up to 4,000 bytes– VARCHAR2(15) – up to 15 characters

• DATE/TIME– Date & Time data– DATE – DD-MON-YY (Default)– TIME – HH:MN:SE (Default)


• LOBLOB– Large OBject data typeLarge OBject data type

• CLOBCLOB– Long variable length charactersLong variable length characters

• BLOBBLOB– Binary objects – Video, Sound, Binary objects – Video, Sound,

GraphicsGraphics• BFILEBFILE

– Reference to an OS fileReference to an OS file– Up to 4GB of data per fileUp to 4GB of data per file



• SQL: Structured Query Language– Command-driven, nonprocedural

language– Origin: IBM, System R, Mid-1970s,

SEQUEL (SQL)– Adopted by Oracle in late 1970s

• Before IBM product– State of the art (state of the art does not

mean ideal)


• SQL Standards

– Major standards organizations work together

• American National Standards Institute (ANSI)

• International Organization for Standardization (ISO)


• SQL Standards– More than 25 approved and current

standards• SQL language: verbs, concepts,

clauses, operations• Embedding SQL in host language• Persistent stored modules (stored

procedures)• SQL routines using JAVA• On-Line analytical processing


• Structured Query Language

– DDL – Data Definition Language

• CREATE

• DROP

• ALTER



– DML – Data Manipulation Language

• SELECT

• INSERT

• DELETE

• UPDATE



– DCL – Data Control Language

• GRANT

• REVOKE


• Characteristics of SQL– Capabilities to

• Define database objects – DDL–Tables, Views, Indexes, Users,

Constraints• Manipulate Data – DML

–Query capability based on relational algebra set operations

–Update capability• Control Data - DCL


• Characteristics of SQL

– Intended for use by

• DBA

• Application Developers

• Some End Users

– SQL is easily grasped, but not quickly mastered (Croft, 1990)


• Example: DEPT table

DEPTNO DNAME LOC

10 ACCOUNTING CHICAGO

20 RESEARCH LONDON

30 SALES LOS ANGELES

40 OPERATIONS BOSTON

DEPTEMPLOYEE

DEPARTMENT

Supervises

Works for


EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

7369 SMITH CLERK 7902 17-DEC-1998 800 20

7499 ALLEN SALESMAN 7698 20-FEB-2000 1600 300 30

7521 WARD SALESMAN 7698 22-FEB-1998 1250 500 30

7566 JONES MANAGER 7839 02-APR-1995 2975 20

7654 MARTIN SALESMAN 7698 28-SEP-1997 1250 1400 30

7698 BLAKE MANAGER 783901-MAY-

19932850 30

7782 CLARK MANAGER 7839 09-JUN-1999 2450 10

7788 SCOTT ANALYST 7566 09-DEC-1996 3000 20

7839 KING PRESIDENT17-NOV-

19915000 10

7844 TURNER SALESMAN 7698 08-SEP-1992 1500 0 30

7876 ADAMS CLERK 7788 12-JAN-1997 1100 20

7900 JAMES CLERK 7698 03-DEC-1999 950 30

7902 FORD ANALYST 7566 03-DEC-1994 3000 20

7934 MILLER CLERK 7782 23-JAN-2000 1300 10

EMP

• Example: EMP table


• Table Definition: ANSI SQL– CREATE TABLE DEPT

• (deptno NUMBER(2) NOT NULL,• dname VARCHAR2(14),• loc VARCHAR2(13)

DEFAULT ‘Key West’);


• Table Definition: ANSI SQL– CREATE TABLE EMP

• (empno NUMBER(4) NOT NULL,• ename VARCHAR2(10),• job VARCHAR2(10),• mgr NUMBER(4),• hiredate DATE,• sal NUMBER (7,2),• comm NUMBER (7,2),• deptno NUMBER(2) NOT NULL);

End 10-10-05


• Data Definition Statements– Define Table structure and constraints– CREATE TABLE makes entries in the data dictionary

• Table Name• Attributes

– Name, Datatype, Size, Nullability• Constraints

– Primary Key– Foreign Key– Check Clause

– ALTER TABLE updates the data dictionary• Adds or modifies attributes• Adds or modifies constraints

– DROP TABLE removes entries from the data dictionary


• The System Tables– Also called data dictionary, catalog– System tables are tables – just like the

data tables• For example:

–user_tables–user_constraints–user_indexes


• The System Tables

– System tables are queried by DBAs and Users via SQL

• DBAs can write procedures, reports using system tables

• Graphical DBA tools generate SQL to access the dictionary


• The System Tables

– RDBMS accesses the system tables on every SQL request

• Updated by DDL statements

• Referenced on DML statements


• SQL: SELECT is used for all queries

– SELECT Data Items

– FROM Table(s)

– WHERE Condition is True


• Manipulation: SELECT Example– Example 01:

• SELECT *• FROM EMP• WHERE job = ‘ANALYST’;

• ResultsEMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

7788 SCOTT ANALYST 7566 09-DEC-1996 3000 20

7902 FORD ANALYST 7566 03-DEC-1994 3000 20



• SELECT ename, job, hiredate• FROM EMP• WHERE hiredate > ’31-DEC-99’;

• ResultsENAME JOB HIREDATE

ALLEN SALESMAN 20-FEB-2000

MILLER CLERK 23-JAN-2000



• SELECT empno, ename, loc• FROM EMP, DEPT• WHERE emp.deptno = dept.deptno• AND loc = ‘CHICAGO’;• Results

EMPNO ENAME LOC

7782 CLARK CHICAGO

7839 KING CHICAGO

7934 MILLER CHICAGO


• Manipulation: SELECT Example– Class Practice 01:– Give me a list of all the salesman and their

managers?

– SELECT ename, job, mgr– FROM EMP– WHERE job = ‘SALESMAN’;


• Manipulation: SELECT Example– Class Practice 02:– Give me a list of all clerks to include their employee

number, manager, hiredate and salary for those who make more than $1000?

– SELECT empno, ename, mgr, hiredate, sal– FROM emp– WHERE job = ‘CLERK’ AND sal > 1000;


• Manipulation: SELECT Example– Class Practice 03:– Give me a list of employees who work in the

accounting department including their salaries?

– SELECT ename, sal, dname– FROM emp, dept– WHERE emp.deptno = dept.deptno – AND deptno = 10;


• SELECT is used to Read Data– User “Designs” the query

• Expresses it according to SQL syntax– One SELECT query can request multiple

relational algebra operations• SELECT …. which columns• FROM …. which tables• WHERE …. which rows

– Each SELECT query is optimized• Transformed into a query execution plan


• SQL: SELECT…ORDER BY– SELECT Data Items– FROM Table(s)– WHERE Condition is True– ORDER BY Data Item [DESC |

ASC]– Presents the result set in sorted order


• SQL: SELECT…ORDER BY– Example:– SELECT empno, ename, sal– FROM emp– WHERE sal > 2500– ORDER BY sal;

EMPNO ENAME SAL

7698 BLAKE 2850

7566 JONES 2975

7788 SCOTT 3000

7902 FORD 3000

7839 KING 5000


• SELECT can present Derived Values– List all the analysts, showing their annual

compensation– SELECT empno, ename, 12*sal– FROM emp– WHERE job = ‘ANALYST’;

EMPNO ENAME 12*SAL

7788 SCOTT 36000

7902 FORD 36000

End 10-12-05


• SQL Subqueries– Suppose we want to find out who makes

more money than Jones• We could first find out Jones’ salary• Then find all employees whose salary is

greater than that• Alternatively…SQL allows nesting

subqueries


• SQL Subqueries– Example:– SELECT empno, ename– FROM emp– WHERE sal >

• (SELECT sal• FROM emp• WHERE ename = ‘JONES’);

• The subquery is executed first


• Updating the Database– INSERT

• Append new rows to a table• Example:• INSERT INTO dept (deptno, dname, loc)• VALUES (40, ‘OPERATIONS’,

‘BOSTON’);


• Updating the Database– DELETE

• Removes one or more rows from a table• Example:• DELETE FROM dept• WHERE loc = ‘DETROIT’;


• Updating the Database– UPDATE

• Replaces values in one or more columns• Example:• UPDATE emp• SET sal = sal * 1.10• WHERE ename = ‘MILLER’;


• SQL Query and Manipulation Summery (ANSI Standard)

• Reading– SELECT

• Updating– INSERT– DELETE– UPDATE



• Grouping– GROUP BY– HAVING

• Sequencing– ORDER BY



• Built-in Functions– MIN– MAX– SUM– AVG– COUNT– DISTINCT



• Special Operators– NOT, AND, OR– BETWEEN, NOT BETWEEN– IN, NOT IN– LIKE, NOT LIKE– IS NULL, IS NOT NULL



• Arithmetic Operators– +– -– /– *



• Comparison Operators– =– <> (not equal)– <– >– <=– >=


• Views– Purpose of Views

• Simplify• Function• Security


• View Definition– CREATE VIEW view_name AS

• SELECT data_items• FROM table(s)• WHERE condition is true

– View definition is saved in system tables– View is a Virtual Table

• Database is accessed only when view is referenced


• View Definition Cont’d– Each user “sees” the database through their

view as if• It is only one table• It contains only the data items of interest• The data items of interest have that user’s

names• The data items are in exactly the order

desired• Multiple views can be based on the same

table


• View Example– Create a view for the accounting department

to include: empno, ename, position, ancomp• CREATE VIEW acct (empno, ename,

position, ancomp) AS–SELECT empno, ename, job,

12*(sal+nvl(comm, 0))–FROM emp;


• View Example– List all the analysts showing their annual

compensation• SELECT *• FROM acct• WHERE position = ‘ANALYST’;

– Here the Query and View are merged for query execution


• Updating through Views– Update through view modifies data in the

underlying table• Updates can be made through views

based on one table• Updates can sometimes be made through

views based on more than one table– UPDATE acct– SET position = ‘SALESMAN’– WHERE ename = ‘JAMES’;


• Database Security is based on Password and Authorizations– Need is to protect the database from unauthorized

users– Authorization is granted to individual users to

• Access (log on to) the DBMS• Access specified attributes in the database• Execute specified operations on each attribute

– The DBA is responsible for Passwords, and Authorizations


• The Role of the DBA– DBA privileges vary greatly from product to

product– Users can GRANT privileges on a table

provided:• User is the owner, executed CREATE

TABLE for that table or• User was granted privileges WITH

GRANT OPTION


• The Role of the DBA– DBA has permissions to execute other

statements• Can CREATE, DROP, or ALTER users,

user profiles, tablespaces, tables, etc– Some installations create a hierarchy of

DBAs• Entire Database• Application area DBAs

– Good practice is to create a user_id for each specific DBA role


• DCL – Data Control Language – Commands:

• GRANT• REVOKE


• Security and SQL– GRANT statement

• GRANT privileges• ON a table or view• TO a user• (WITH GRANT OPTION)

– REVOKE statement• REVOKE privileges• ON a table or view• FROM a user


• ANSI SQL GRANT privileges– ALL– SELECT– INSERT– UPDATE– DELETE– CONNECT


• See Example data for Employee & Departments:– Let Miller read all of the EMP table– Part 01

• GRANT Connect• TO miller• IDENTIFIED BY 382miller;

– Part 02• GRANT Select• ON emp• TO miller;


• See Example data for Employee & Departments:– Let Jones read and update the data for

employees in her department– Part 01

• CREATE VIEW jones AS• SELECT *• FROM emp• WHERE mgr = 7566;


• See Example data for Employee & Departments:– Part 02

• GRANT Select, Update• ON jones• TO jones;


• See Example data for Employee & Departments:– Let King read the data for all employees in

the emp table and update the salary, commission, and job attributes.• GRANT Select, Update(sal, comm, job)• ON emp• TO king;


• Database Security:– Security is a mentality– Security is environment-specific– The DBA has a key role

• Builds the database• Grants user/password access into DBMS• Defines user views• Grants user access and authorization to data

– 95% of all security violations can be avoided by attention to detail

• Change master passwords after installation• Change passwords frequently


• Questions?

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IT 20303 The Relational DBMS Section 07. Relational Database Theory Using a Relational DBMS.

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