Ashish Raghute, IT Director, Fleetwood Enterprises Introduction to RDBMS and SQL.

Ashish Raghute, IT Director, Fleetwood Enterprises

Introduction to RDBMS and SQL

Introduction to RDBMS and SQL 7:30 am – 9 am

1. General RDBMS Concepts - Relational Vs. File Systems, normalization, ERD, extensibility

2. SQL DDL (Data definition language) Create, Alter, Drop Tables and Indexes, typical data types, space implications, referential integrity

9.15 am – 10.30 am

3. SQL DML (Data manipulation language) - selection, projection, aggregates, inner/outer/self/recursive/nested/co-related, updates, inserts, index use, statistics use, best practices and tips

4. Vendor enhancements to SQL - example SQL*PLUS and iSQL, functions (string, math, date etc.)

5. Examples of some tough SQLs for selects, inserts, updates and deletes

10.35 am – 11.30 am

6. Setting up ODBC

7. Exercises for the week


RDBMS – Relational Database Management System

Chronology:• Simple file based system• Sophisticated file based systems like VAX/RMS with COBOL • DBMS – Database • Next generation of DBMS – e.g. Paradox, DBaseIII..• DBMS typically had an engine and 4GL tool set• Relational DBMS is the most popular data access technology today• OODBMS not so popular

Typical RDBMS Features:• Normalization• Strong 4GL language support• Optimization – Indexing, Caching, execution planning etc.



Flat Files vs. Relational Databases

Flat file is "A relatively simple database system in which each database is contained in a single table (or two). In contrast, relational database systems use multiple tables to store information, and each table can have a different record format.” - ZDNet’s Definition.

Examples Scenario – Order Entry System

File Database design:Cust Name, Cust Address, Order Date, Order Header, Item 1, Qty 1, Price1, Item 2, Qty 2, Price2, Item 3,………

RDBMS

Customer Table : Name, Address ……Order Table: Link to Customer Table, Order Header ….Order Item Table: Link to Order Table , Qty, Link to Product Table ….Product Table: Product Name, Cost, Price, On Hand Qty …..

Suggested Reading on Normalization


http://www.sqlmag.com/Articles/Index.cfm?ArticleID=4887&pg=1


Customer Order Order Item

Product

Entity Relationship Diagram or ERD for 3RD Normal Form

Entity

Customer.Customer_Num = Order.Customer_Num

Primary Key Foreign Key

1 to Many (1:M)Customer can have minimum zero and max many/unlimited ordersOrder can have minimum one and maximum one Customer

Attributes are all non-Key fields of an entity (typically one table)Hierarchical table design example, employee-manager



What is Normalization ?

• Arranging data into logical groupings such that each group describes a small part of the whole;

• minimizing the amount of duplicate data stored in a database; • organizing the data such that, when you modify it, you make the

change in only one place; • building a database in which you can access and manipulate the

data quickly and efficiently without compromising the integrity of the data in storage.



Example of poorly normalized table



Example of well normalized tables in 3NF



Extensibility - Commonly observed poorly designed tables:

1. Employee, Manager1, Manager2, Manager3

What will happen if a fourth manager comes into picture? What if 99% of employees have only one manager?

2A. Order Number, Part Number, Part Description2B. Part Number, Part Description

What if Part Description needs to be changed?

3A. Candidate Name, Address ….3B. Masters Degree College, Graduation Year, Under-grad college,

under-grad year, high school, high school year

Several candidates will have only high-school though a few will have Masters



Getting started quickly on SQL:

SQL*Plus is the most commonly used program to work with Oracle Database

Another commonly used program is SQLPLUS Worksheet

We will use SQL*Plus for this session



Starting SQL*Plus


2. SQL DDL

Before we begin, common, useful commands for Oracle (NON-ANSI):

•Select * from tab;

•Describe <TableName>

•Select sysdate from DUAL;


Data Definition Language is used to create Tables, Indexes, Views, Sequences, DB Links, Tablespaces etc..

• Creating a table (click here for suggested reading):

Create table TableName ( ColumnName1 int, ColumnName2 char(10), ColumnName3 varchar2(20), ColumnName4 Long);

Create table TableName as Select ColumnName1, ColumnName2….. from ExistingTable;

2. SQL DDL

Exercise – Create a set of tables in 3rd Normal Form (3 or 4 tables). Use as many data-types as you can. Note that only one Long field is allowed per table (how will you solve this problem, if you need more than 1?).

Suggested Reading click (here)


http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/statements_73a.htm

http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/sql_elements2a.htm

http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/sql_elements2a.htm

Some tips

• After any DDL, transactions are always committed• Advance table creation options with tablespaces, extent sizes etc. • Indexes – guidelines on creation, statistics, sizing, composite index

use• Sequence Object – its use, avoidable problems• Database Links• Referential Integrity

2. SQL DDL

Recreate the tables you created to add a few referential integrity checks.

Suggested Reading click (here)




9.15 am – 10.30 am

3. SQL DML (Data manipulation language) - selection, projection, aggregates, inner/outer/self/recursive/nested/co-related, updates, inserts, index use, statistics use, best practices and tips

4. Vendor enhancements to SQL - example SQL*PLUS and iSQL, functions (string, math, date etc.)

5. Examples of some tough SQLs for selects, inserts, updates and deletes


Employee Table = Emp_Id, Emp_Fname, Emp_Lname, Age, Salary

3. SQL DML (Data manipulation language)

Select Emp_Id, Age, Salary From EmployeeWhere Salary < 2000 and Age > 30;

SELECTION

PROJECTION

SELECTION & PROJECTION

To select all fields, we can use “*”. For example, Select * from Employee

To select all rows, just drop the WHERE clause


Select Emp_Id, Age, Salary From EmployeeWhere Salary < 2000 and Age > 30Order by Salary, Age Descending;

Employee Table = Emp_Id, Emp_Fname, Emp_Lname, Age, Salary


ORDER BY


Select A.Emp_Id, A.Age, B.Company_Name From Employee A, Company BWhere A.Company_id = B.Company_Id and A.Age > 30Order by A.Age Descending;

Employee Table = Emp_Id, Emp_Fname, Emp_Lname, Age, Company_IDCompany Table = Company_Id, Company_Name


SIMPLE (PLAIN or INNER) JOIN

Note: Result set is a Cartesian product of number of rows from each table

Be careful to ensure all tables are joined correctly


SOME COMMON EXAMPLES ARE COUNT, SUM, AVG etc.


AGGREGATE FUNCTIONS

Common mistake – Group by is used even if there is no aggregate function in select

Select AVG(A.Age), B.Company_Name From Employee A, Company BWhere A.Company_id = B.Company_Id andGroup by B.Company_NameOrder by 1;





DISTINCT

Note – Distinct should be used very rarely. Need to use Distinct often is indicative of a bad application design

Select distinct Company_Name From Company;

Select count (distinct Company_Name) From Company;





“HAVING” CLAUSE

Having clause is like a Where clause for Aggregate attributes

Select AVG(A.Age), B.Company_Name From Employee A, Company BWhere A.Company_id = B.Company_Id andGroup by B.Company_NameHaving AVG(A.Age) > 20



Significance of NULL value

To compare a column to NULL, use “IS NULL” or “IS NOT NULL” instead of “=NULL” or “!=NULL” because comparison with NULL will always evaluate to FALSE

Example – Select * from Employee where Age is NULL;

NVL Function is another way to compare NULLS

Example – Select * from Employee where NVL(Age,0) = 0;



Operators and Expressions in SQL

Suggested Reading



http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/toc.htm

Self referencing joins

Suggested Reading

select employee_name, mgr_name, level from employee connect by prior employee_name= Mgr_name

Note to myself: Demo this in conv@siebel3_fltux5



http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/queries4a.htm

Standard ANSI SQL and Oracle Compliance

Suggested Reading



http://lbdwww.epfl.ch/f/teaching/courses/oracle9i/server.920/a96540/ap_standard_sql.htm

Sub Queries

Select a.last_name, a.fst_name from s_contact a where a.last_name in (select b.last_name from s_prospect)

Co-related Sub Queries

Select a.last_name, a.fst_name from s_contact a where a.pr_addr_id in (select b.row_id from s_addr_per b where b.per_id = a.row_id)



Exists clause

Select * from contacts A where exists (select 1 from Orders B where B.contact_id=a.contact_id)

Not Exists

Select * from contacts A where not exists (select 1 from Orders B where

B.contact_id=a.contact_id)



InsertUpdate

Insert examples insert into Contact (Fst_name, Last_name) values (‘John’, ‘Smith’);

insert into Contact values (‘John’, ‘Smith’….);

insert into Contact (Fst_name, Last_name) select First, Last from AnotherContactTable;

Update examples Update Contact set Fst_Name=Last_Name where Fst_Name is

null;

Update Contact set Fst_Name = ‘Cliff’ where last_name=‘Luchsinger’;

Update Contact A set A. Company_id = (select b.company_id from

Company B where A.phone_number=b.phone_number);



DeleteTruncate

Delete examples Delete from Contact where last_upd < sysdate – 5*365 ;

Delete Contact where last_upd < sysdate – 5*365 ;

Delete Contact A where not exists (select 1 from Orders B where B.contact_id=A.contact_id);

Truncate example Truncate table Contact



“Decode” function in Oracle

Select Event, Year, decode(Month, 1, ‘Jan’, 2, ‘Feb’,….11,’Nov’,’Dec’) from History;

Decodes can be nested.

4. Vendor enhancements to SQL – Some Example

SQL Server has an equivalent function called iff.


Problem – You forgot to create unique indexes on a table and by mistake, duplicate records got loaded. Even the primary keys are dups. You need to clean up the table such that only one record is left behind.

Delete DupTable A where A.Rowid < (select max(B.Rowid) from DupTable B where b.primary_key=a.primary_key);

5. Example of a tough SQL


Setup one data source. Connect to this datasource using MS-ACCESS

6. Set-up ODBC


See your training folder for the “exercises-RDBMS, SQL, PLSQL.ppt”

7. Exercises


About the Author

Ashish Raghute currently works as the IT Director at Fleetwood

Enterprises, Inc. , USA’s leader in recreational vehicle sales and a leading producer and retailer of manufactured housing. Prior to joining Fleetwood, Ashish was a Principal at IBM Business Consulting Services and Principal Consultant at PricewaterhouseCoopers Consulting. For more than 15 years, Ashish has guided companies of various sizes from dot net startups to Fortune 1000 to successfully realize their IT vision in the areas of CRM, ERP, Data Warehousing and E-Business. Ashish can be contacted via email at [email protected].

Ashish Raghute, IT Director, Fleetwood Enterprises Introduction to RDBMS and SQL.

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