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Lecture8: Relational Algebra, Data Manipulation in SQL , Simple SQL queries Ref. Chapter4&5 1 College of Computer and Information Sciences - Information Systems Dept. Prepared by L. Nouf Almujally & Aisha AlArfaj IS220 : Database Fundamentals
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Lecture8: Relational Algebra, Data Manipulation in

SQL , Simple SQL queries

Ref. Chapter4&5

1

Coll

ege

of

Com

pute

r an

d I

nfo

rmat

ion S

cien

ces

-In

form

atio

n S

yst

ems

Dep

t.

Prepared by L. Nouf Almujally & Aisha AlArfaj

IS220 : Dat abase Fundament a l s

The Process of Database Design

Real World Domain

Conceptual model (ERD)

Relational Data Model

Create schema

(DDL)

Load Data

(DML)

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Tables in the Examples

Customer(custNo, custName, custSt, custCity, age)

Product(prodNo, prodName, prodDes, price)

Orders(ordNo, ordDate, custNo, prodNo, quantity)

Where

custName, custSt, custCity, prodName, prodDes are strings

ordDate is date

Others are numbers

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Sample Data in Customer Table

custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

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Sample Data in Product Table

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy Food 100

102 P2 200

103 P3 self_raising

flour,80%wheat

300

104 P4 network 80x 300

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Sample Data in Orders Table

ordNo ordDate custNo prodNo quantity

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

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Relational Algebra

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Relational Algebra

• Operations on relations (sets of records) to produce a relation as result.

• The output from one operation can become the input to another operation (nested relational algebra)

• Eight fundamental operations in relational algebra:

Unary operations: work on one relation

Selection

Projection

Binary operations: work on pairs of relations

Cartesian product Join

Union Intersection

Set difference Division

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Algebra Operators

abc

xy

aabbcc

xyxyxy

Cartesian Product

a1a2a3

b1b2b3

b1b2b3

c1c2c3

a1a2a3

b1b2b3

c1c2c3

Join

xy

aaaabc

xyzxy

Divide

Selection Project

Union Intersection Difference

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Selection Operation

• Select[cond](R)- selects tuples out of relation R that meet specified condition cond to result in a new relation.

• Denoted by ⱷ (R)

Where R is the relation and ⱷ is the logical condition

• Example:

List all products which are priced more than 100.

price > 100 (product)

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prodNo prodName prodDes price

102 P2 200

103 P3 self_raising

flour,80%wheat

300

104 P4 network 80x 300

Examples

Example 1: Find all orders of product 100 before 02/01/03.

(prodNo = 100) AND (ordDate <'02-jan-2003‘ ) (orders)

Example 2: Find all products priced less than 200 or greater than 300.

(price < 200 ) OR (price >300) (product)

ordNo ordDate custNo prodNo quantity

1 01-jan-2003 1 100 2

4 01-jan-2003 3 100 2

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy food 100

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Projection Operation

• Project[attr-list](R) - selects columns specified in the attributes list out of R to result in a new relation.

• Denoted by < attribute list> (R)

• Example:

List prodNo and price of all products.

prodNo, price(product)

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prodNo price

100 100

101 100

102 200

103 300

104 300

Examples

Example 1: List all products (by prodNo and price) which are priced more than 100.

prodNo, price( price > 100 (product))

Example 2: What is the name of the customer whose custNo is 1?

custName ( custNo=1 (customer))

prodNo price

102 200

103 300

104 300

custName

C1

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Data Manipulation language ( DML)

Data Manipulation Language (DML)

• DML is used to retrieve and modify data in the tables

• Four basic statements

• Insert Into

• Select

• Update

• delete From

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Insert Statement

• The INSERT statement adds one or more new rows of data to a database table.

• Syntax

• Note:• value list must correspond to column list

• If column list is omitted, then a value for every attribute is required

• The data types must be correct

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INSERT INTO table_name (column1,column2,column3,...)

VALUES (value1,value2,value3,...);

INSERT INTO table_name

VALUES (value1,value2,value3,...);

• Example: for table Customer,

Insert into Customer(custNo, custName) values (6, 'John');

Output: 1 row inserted

Insert into Customer values (7, 'David ', 'St1','City1', 20);

Output: 1 row inserted

Insert Statement Example

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Simple SELECT Queries

• The SELECT command is used for submitting queries to the DBMS.

• Syntax

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SELECT expression_listFROM table_list

[WHERE condition][ORDER BY expression_list];

Simple SELECT Queries

Expression in SELECT statement :

Condition in WHERE statement:

• an expression that can be evaluated to TRUE or FALSE.

• Only rows satisfying the condition will be chosen.

• Condition can be simple comparison or compound expression

Expression Example

column names SELECT prodNo

arithmetic operators for numbers: +, -, *, / SELECT Price+10

Constant SELECT 'The first name is', fnameFROM customer

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Conditions in the WHERE Clause

WHERE clause consists of five basic search conditions:

• Comparison: Compare the value of one expression to the value of

another expression (= , <, >, <=, >=, <>).

• Range: Test whether the value of an expression falls within a specified

range of values (BETWEEN/ NOT BETWEEN).

• Set membership: Test whether the value of an expression equals one of

a set of values (IN/ NOT IN).

• Pattern match: Test whether a string matches a specified pattern (LIKE/

NOT LIKE).

• NULL: Test whether a column has null value (IS NULL/ IS NOT NULL).

Note: Basic comparisons can be compounded by AND, OR, NOT

• Eg, prodNo=100 and ordDate='01-jan-2003'

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Simple Queries : Comparison search condition

Comparison operators: = , < , > , <= , >= , <>

Example 1: List all products (by prodNo and price) which are priced more than 100.

Select prodNo, priceFrom Product

Where price >100;

Example 2: What is the name of the customer whose custNo is 1?

Select custNameFrom customer

Where custNo=1;

prodNo price

102 200

103 300

104 300

custName

C1

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Listing All Data in a Table

• If WHERE clause is omitted, all rows will be listed.

Example: List all data in the customer table

SELECT custNo, custName, custSt, custCity, age

FROM customer;

OR (use * for all columns)

SELECT * FROM CUSTOMER;

custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd

Riyadh 25

4 C4 Mains Rd

Dammam

5 C5 Mains Rd

Riyadh

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Simple Queries : Compound comparison search condition

• Compound comparison operators: AND , OR , NOT , ( )

• Order of evaluation:• Expression is evaluated left to right

• Between brackets

• NOT

• AND

• OR

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Examples

Example 1: Find all orders of product 100 before 02/01/03.SELECT *

FROM ordersWHERE prodNo = 100 AND ordDate <'02-jan-2003';

Example 2: Find all products priced less than 200 or greater than 300

SELECT * FROM product

WHERE price < 200 OR price >300;

ordNo ordDate custNo prodNo quantity

1 01-jan-2003 1 100 2

4 01-jan-2003 3 100 2

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy food 100

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More Examples

Example: Find the customer with name C1 and live in Riyadh or Jeddah

SELECT *

FROM customers

WHERE custName ='C1‘ AND (custCity='Jeddah' OR custCity='Riyadh');

custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

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Simple Queries : BETWEEN / NOT BETWEEN

• The BETWEEN operator is used to select values within a range.

• The NOT BETWEEN checks if a value is outside a range.

• Syntax:

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SELECT column_name(s)

FROM table_name

WHERE column_name BETWEEN |NOT BETWEEN

value1 AND value2;

BETWEEN Example

Example: List products priced between 200 and 300.

SELECT *

FROM product

WHERE price >=200 and price <=300;

or equivalently

SELECT *

FROM product

WHERE price between 200 and 300;

prodNo prodName prodDes price

102 P2 200

103 P3 self_raisingflour,80%wheat

300

104 P4 network 80x 300

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Simple Queries : IN / NOT IN

• IN tests whether a data value matches one of a list values.

• NOT IN checks for data values that do not lie in a specific list of values

• Syntax

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SELECT column_name(s)

FROM table_name

WHERE column_name IN| NOT IN (value1,value2,...);

IN Example

Example: List all customers living in Riyadh, or Dammam, or Jeddah.

SELECT *

FROM Customer

WHERE custCity = 'Jeddah' OR custCity = 'Riyadh' OR

custCity = 'Dammam';

or equivalently

SELECT *

FROM Customer

WHERE custCity IN (‘Jeddah', ‘Riyadh', ‘Dammam');

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custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Simple Queries : LIKE / NOT LOKE

• LIKE is used to search for a specified pattern in a column.

• NOT LIKE allows you to select records that does NOT match the pattern.

• Syntax

• SQL has special pattern matching symbol

• % represents any sequence of zero or more characters

• _ represents any single character

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SELECT column_name(s)

FROM table_name

WHERE column_name LIKE | NOT LIKE ‘pattern’;

LIKE Example

Example: List all products whose description contain the string 'Food'.

SELECT *

FROM product

WHERE prodDes LIKE '%Food%';

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy food 100

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More Examples of LIKE | NOT LIKE

LIKE 'H_' : any string beginning with H and exactly 2 characters long

NOT LIKE 'H%': any string not beginning with H

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Simple Queries : IS NULL and IS NOT NULL

• It is not possible to test for NULL values with comparisonoperators, such as =, <, or <>.

• To test for null values in a query, use IS NULL or IS NOT NULL inthe WHERE clause.

• Comparisons between a NULL and any other value, returnunknown and the result will not be included in the final results

• Syntax

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SELECT column_name(s)

FROM table_name

WHERE column_name IS NULL | IS NOT NULL ;

IS NULL and IS NOT NULL Examples

Example: List all products with a product description.

SELECT *

FROM product

WHERE prodDes IS NOT NULL;

Similarly, to list products without description, use

SELECT *

FROM product

WHERE prodDes IS NULL;

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy Food 100

103 P3 self_raisingflour,80%wheat

300

104 P4 network 80x 300

prodNo prodName prodDes price

102 P2 200

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Simple Queries : Use of DISTINCT

• Use Distinct in the select statement To remove duplicate values

• Syntax

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SELECT DISTINCT column_name,column_name

FROM table_name;

Use of DISTINCT Example

Example: List all customer cities.

SELECT custCity FROM customer;

• A city will be repeated if there are more than one customer in that city. To eliminate the duplicates, use:

SELECT DISTINCT custCity FROM customer;

custCity

Jeddah

Riyadh

Dammam

custCity

Jeddah

Riyadh

Riyadh

Dammam

Riyadh

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Simple Queries : Ordering of Rows

• Rows can be put in ascending or descending order of some columns. To do this, use ORDER BY

• Syntax

• Default order (ie, if desc is not used) is ascending

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SELECT column_name,column_name

FROM table_name

WHERE Condition

ORDER BY column_name,column_name ASC|DESC ;

Ordering of Rows Example

• Example: list all products in descending order of price

SELECT *

FROM product

ORDER BY price desc;

• Can also order by several attributes, eg.

ORDER BY price desc, prodName;

prodNo prodName prodDes price

103 P3 self_raisingflour,80%wheat

300

104 P4 network 80x 300

102 P2 200

100 P0 Food 100

101 P1 healthy Food 100

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Ordering of Rows Example

SELECT * FROM Individual

ORDER BY FirstName, LastName ;

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Operators summary

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Operator Function

= equal to

< less than

> greater than

<= less than equal to

>= greater than equal to

<> not equal to

LIKE % used as wildcard. eg. LIKE ‘%PRE%’

IN test for in an enumerated list.

BETWEEN used to select values within a range

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Update Statement

• The UPDATE statement is used to update records in a table

• Syntax

Notice the WHERE clause in the SQL UPDATE statement!The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!

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UPDATE table_name

SET column1=value1, column2=value2,...

WHERE some_column=some_value ;

Update Statement Example

• Example : Customer C1 has changed his city to Riyadh.

UPDATE CustomerSET custCity=‘Riyadh‘ , custSt='12 Mains Rd'

WHERE CustName=C1';

Output: 1 row updated

Select * From Customer ;

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custNo custName custSt custCity age

1 C1 12 Main Rd Riyadh 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Update Statement Example

Be careful when updating records. If we had omitted the WHERE clause, in the example before, like this:

UPDATE CustomerSET custCity=‘Riyadh‘ , custSt='12 Mains Rd' ;

Output: 5 rows updated

Select * From Customer ;

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custNo custName custSt custCity age

1 C1 12 Main Rd Riyadh 20

2 C2 12 Main Rd Riyadh 30

3 C3 12 Main Rd Riyadh 25

4 C4 12 Main Rd Riyadh

5 C5 12 Main Rd Riyadh

Delete Statement

• The DELETE statement is used to delete records in a table.

• Syntax

Notice the WHERE clause in the SQL DELETE statement!The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!

DELETE does not delete the table itself, only

rows in the table.

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DELETE FROM table_name

WHERE some_column=some_value;

Delete Statement Example

• Example : Delete Customer C1

DELETE FROM CustomerWHERE CustName=‘C1';

Output: 1 row deleted

Select * From Customer ;

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custNo custName custSt custCity age

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Delete Statement Example

• Example : Delete all Customers

DELETE FROM Customer;

Output: 5 row deleted

Select * From Customer ;

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custNo custName custSt custCity age

Truncate Statement

• TRUNCATE deletes all data in a table and frees storage space for the table rows ( deletes data faster but you cannot rollback)

• Syntax

TRUNCATE get rid of the data but not the table itself (DROP)

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Truncate table table_name;

Truncate Example

• Example : Delete all Products

TRUNCATE TABLE product;

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prodNo prodName prodDes price

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Truncate vs Delete

Delete Truncate

To remove rows from a table To remove all rows from a table

WHERE Clause can be used , if no where clause is specified all

rows will be removed

We cant use WHERE clause

DML command DDL command

You can rollback You can’t rollback

Extra Example

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Employee No. First Name Last Name Dept Number Salary

E1 Mandy Smith D1 50000

E2 Daniel Hodges D2 45000

E3 Shaskia Ramanthan D2 58000

Dept Number Dept Name Location Mail Number

D1 Computer Science Bundoora 39

D2 Information Science Bendigo 30

D3 Physics Bundoora 37

D4 Chemistry Bendigo 35

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1)Basic SQL SELECT Queries

SELECT firstName, lastName

FROM Employee

WHERE employeeNo = ‘E1’;

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2)Compound Comparison

SELECT deptNumber

FROM EMPLOYEE

WHERE lastName = ‘Smith’OR lastName = ‘Hodges’;

SQL Queries Example

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SELECT DISTINCT deptNumber

FROM EMPLOYEE;

3)Duplicate Removal

4)Set Membership Search ( IN)

SELECT deptNumber, mailNumber

FROM DEPARTMENT

WHERE deptName IN ( ‘Computer Science’, ‘Physics’);

SQL Queries Example

5)Pattern Match Search ( LIKE)

SELECT employeeNo, deptNumber

FROM EMPLOYEE

WHERE firstName LIKE ‘%an%’;

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SELECT employeeNo , lastName

FROM EMPLOYEE

ORDER BY lastName;

6)Sorting Output from Queries

SQL Queries Example

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Relation Algebra Queries Example

Rewrite queries 1, 2, and 4 by using the ralational

algebra

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References

• “Database Systems: A Practical Approach to Design, Implementation and Management.” Thomas Connolly, Carolyn Begg. 5th Edition, Addison-Wesley, 2009.

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