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Lecture 25Lecture 25
Enterprise
Systems
Development( CSC447)
COMSATS Islamabad
Muhammad Usman, Assistant Professor
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7
Service-oriented design: design sub-stepsService-oriented design: design sub-stepsService orientedanalysis
Service orienteddesign
Compose SOA
Design entity-centric business services
Design infrastructure services
step 3
step 2
step 1
...
Design task-centricbusiness services
step 4
Design SO business process
step 5
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8
Entity-centric business servicesEntity-centric business services
Customer
PO
Employee
Invoice
Order
1
**
1
1
1
*
*
1
1
1
*
*
1
*EmailWeekly hours
CustomerHours billed
...
...
...
Goal: entity-centric business service layer + parent orchestration layer
Receive PO document
PO processingservice
Validate PO document
(If PO document is invalid,)send rejection notification (and end process)
Transform PO document into native electronic PO format
<<include>>
<<include>>
...
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9
Infrastructure servicesInfrastructure services
Infrastructure service layer
Business service layer
Orchestration/coordination layer
POprocessingservice
POservice
Notificationservice
VerifyPOservice
Transformservice
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10
Task-centric business servicesTask-centric business services
UML sequence diagram express and refine order of invocations
implicit in the UML use case diagram
Receive PO document
PO processingservice
Validate PO document
(If PO document is invalid,)send rejection notification (and end process)
Transform PO document into native electronic PO format
<<include>>
<<include>>
...
Verify POservice
POservice
Notificationservice
get_PO[PO data]
send_reject
verify
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DATABASE DESIGNDATABASE DESIGN
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Database Management System (DBMS)Database Management System (DBMS)
DBMS contains information about a particular enterprise
Collection of interrelated data
Set of programs to access the data
An environment that is both convenient and efficient to use
Database Applications:
Banking: all transactions
Airlines: reservations, schedules
Universities: registration, grades
Sales: customers, products, purchases
Online retailers: order tracking, customized recommendations
Manufacturing: production, inventory, orders, supply chain
Human resources: employee records, salaries, tax deductions
Databases touch all aspects of our lives
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Purpose of Database SystemsPurpose of Database Systems
In the early days, database applications were built directly on top of file systems
Drawbacks of using file systems to store data:
Data redundancy and inconsistency
Multiple file formats, duplication of information in different files
Difficulty in accessing data
Need to write a new program to carry out each new task
Data isolation — multiple files and formats
Integrity problems
Integrity constraints (e.g. account balance > 0) become “buried” in program code rather than being stated explicitly
Hard to add new constraints or change existing ones
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Purpose of Database Systems (Cont.)Purpose of Database Systems (Cont.) Drawbacks of using file systems (cont.)
Atomicity of updates Failures may leave database in an inconsistent state with partial
updates carried out Example: Transfer of funds from one account to another should
either complete or not happen at all Concurrent access by multiple users
Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies
– Example: Two people reading a balance and updating it at the same time
Security problems Hard to provide user access to some, but not all, data
Database systems offer solutions to all the above problems
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Levels of AbstractionLevels of Abstraction
Physical level: describes how a record (e.g., customer) is stored.
Logical level: describes data stored in database, and the relationships among the data.
type customer = record
customer_id : string; customer_name : string;customer_street : string;customer_city : string;
end;
View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes.
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View of DataView of Data
An architecture for a database system
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Instances and SchemasInstances and Schemas
Similar to types and variables in programming languages
Schema – the logical structure of the database
Example: The database consists of information about a set of customers and accounts and the relationship between them)
Analogous to type information of a variable in a program
Physical schema: database design at the physical level
Logical schema: database design at the logical level
Instance – the actual content of the database at a particular point in time
Analogous to the value of a variable
Physical Data Independence – the ability to modify the physical schema without changing the logical schema
Applications depend on the logical schema
In general, the interfaces between the various levels and components should be well defined so that changes in some parts do not seriously influence others.
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Data ModelsData Models
A collection of tools for describing Data Data relationships Data semantics Data constraints
Relational model
Entity-Relationship data model (mainly for database design)
Object-based data models (Object-oriented and Object-relational)
Semistructured data model (XML)
Other older models: Network model Hierarchical model
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Data Manipulation Language (DML)Data Manipulation Language (DML)
Language for accessing and manipulating the data organized by the appropriate data model
DML also known as query language
Two classes of languages
Procedural – user specifies what data is required and how to get those data
Declarative (nonprocedural) – user specifies what data is required without specifying how to get those data
SQL is the most widely used query language
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Data Definition Language (DDL)Data Definition Language (DDL)
Specification notation for defining the database schema
Example: create table account ( account_number char(10),
branch_name char(10),
balance integer) DDL compiler generates a set of tables stored in a data dictionary Data dictionary contains metadata (i.e., data about data)
Database schema Data storage and definition language
Specifies the storage structure and access methods used Integrity constraints
Domain constraints Referential integrity (e.g. branch_name must correspond to a
valid branch in the branch table) Authorization
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Relational ModelRelational Model
Example of tabular data in the relational modelAttributes
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A Sample Relational DatabaseA Sample Relational Database
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SQLSQL
SQL: widely used non-procedural language
Example: Find the name of the customer with customer-id 192-83-7465select customer.customer_namefrom customerwhere customer.customer_id = ‘192-83-7465’
Example: Find the balances of all accounts held by the customer with customer-id 192-83-7465
select account.balancefrom depositor, accountwhere depositor.customer_id = ‘192-83-7465’ and
depositor.account_number = account.account_number
Application programs generally access databases through one of
Language extensions to allow embedded SQL
Application program interface (e.g., ODBC/JDBC) which allow SQL queries to be sent to a database
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Database DesignDatabase Design
The process of designing the general structure of the database:
Logical Design – Deciding on the database schema. Database design requires that we find a “good” collection of relation schemas.
Business decision – What attributes should we record in the database?
Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas?
Physical Design – Deciding on the physical layout of the database
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The Entity-Relationship ModelThe Entity-Relationship Model
Models an enterprise as a collection of entities and relationships
Entity: a “thing” or “object” in the enterprise that is distinguishable from other objects
Described by a set of attributes
Relationship: an association among several entities
Represented diagrammatically by an entity-relationship diagram:
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Other Data ModelsOther Data Models
Object-oriented data model
Object-relational data model
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Database Application ArchitecturesDatabase Application Architectures
(web browser)
Old Modern
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Database Management System InternalsDatabase Management System Internals
Storage management
Query processing
Transaction processing
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Storage ManagementStorage Management
Storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.
The storage manager is responsible to the following tasks:
Interaction with the file manager
Efficient storing, retrieving and updating of data
Issues:
Storage access
File organization
Indexing and hashing
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Query ProcessingQuery Processing
1. Parsing and translation
2. Optimization
3. Evaluation
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Query Processing (Cont.)Query Processing (Cont.)
Alternative ways of evaluating a given query
Equivalent expressions
Different algorithms for each operation
Cost difference between a good and a bad way of evaluating a query can be enormous
Need to estimate the cost of operations
Depends critically on statistical information about relations which the database must maintain
Need to estimate statistics for intermediate results to compute cost of complex expressions
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Transaction ManagementTransaction Management
A transaction is a collection of operations that performs a single logical function in a database application
Transaction-management component ensures that the database remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.
Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.
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Overall System Structure Overall System Structure
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History of Database SystemsHistory of Database Systems
1950s and early 1960s:
Data processing using magnetic tapes for storage
Tapes provide only sequential access
Punched cards for input
Late 1960s and 1970s:
Hard disks allow direct access to data
Network and hierarchical data models in widespread use
Ted Codd defines the relational data model
Would win the ACM Turing Award for this work
IBM Research begins System R prototype
UC Berkeley begins Ingres prototype
High-performance (for the era) transaction processing
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History (cont.)History (cont.)
1980s: Research relational prototypes evolve into commercial systems
SQL becomes industry standard Parallel and distributed database systems Object-oriented database systems
1990s: Large decision support and data-mining applications Large multi-terabyte data warehouses Emergence of Web commerce
2000s: XML and XQuery standards Automated database administration Increasing use of highly parallel database systems Web-scale distributed data storage systems
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RELATIONAL MODELRELATIONAL MODEL
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Example of a RelationExample of a Relation
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Attribute TypesAttribute Types
Each attribute of a relation has a name
The set of allowed values for each attribute is called the domain of the attribute
Attribute values are (normally) required to be atomic; that is, indivisible
E.g. the value of an attribute can be an account number, but cannot be a set of account numbers
Domain is said to be atomic if all its members are atomic
The special value null is a member of every domain
The null value causes complications in the definition of many operations
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Relation SchemaRelation Schema
Formally, given domains D1, D2, …. Dn a relation r is a subset of
D1 x D2 x … x Dn
Thus, a relation is a set of n-tuples (a1, a2, …, an) where each ai Di
Schema of a relation consists of
attribute definitions
name
type/domain
integrity constraints
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Relation InstanceRelation Instance
The current values (relation instance) of a relation are specified by a table
An element t of r is a tuple, represented by a row in a table
Order of tuples is irrelevant (tuples may be stored in an arbitrary order)
JonesSmithCurryLindsay
customer_name
MainNorthNorthPark
customer_street
HarrisonRyeRyePittsfield
customer_city
customer
attributes(or columns)
tuples(or rows)
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DatabaseDatabase
A database consists of multiple relations
Information about an enterprise is broken up into parts, with each relation storing one part of the information
E.g.
account : information about accounts depositor : which customer owns which account customer : information about customers
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The The customer customer RelationRelation
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The The depositor depositor RelationRelation
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Why Split Information Across Relations?Why Split Information Across Relations?
Storing all information as a single relation such as bank(account_number, balance, customer_name, ..)results in
repetition of information
e.g.,if two customers own an account (What gets repeated?)
the need for null values
e.g., to represent a customer without an account
Normalization theory deals with how to design relational schemas
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KeysKeys
Let K R
K is a superkey of R if values for K are sufficient to identify a unique tuple of each possible relation r(R)
by “possible r ” we mean a relation r that could exist in the enterprise we are modeling.
Example: {customer_name, customer_street} and
{customer_name}
are both superkeys of Customer, if no two customers can possibly have
the same name
In real life, an attribute such as customer_id would be used instead of
customer_name to uniquely identify customers, but we omit it to keep
our examples small, and instead assume customer names are unique.
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Keys (Cont.)Keys (Cont.)
K is a candidate key if K is minimal
Example: {customer_name} is a candidate key for Customer, since it
is a superkey and no subset of it is a superkey.
Primary key: a candidate key chosen as the principal means of
identifying tuples within a relation
Should choose an attribute whose value never, or very rarely,
changes.
E.g. email address is unique, but may change
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Foreign KeysForeign Keys
A relation schema may have an attribute that corresponds to the primary key of another relation. The attribute is called a foreign key.
E.g. customer_name and account_number attributes of depositor are foreign keys to customer and account respectively.
Only values occurring in the primary key attribute of the referenced relation may occur in the foreign key attribute of the referencing relation.
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Schema DiagramSchema Diagram
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Query LanguagesQuery Languages
Language in which user requests information from the database.
Categories of languages
Procedural
Non-procedural, or declarative
“Pure” languages:
Relational algebra
Tuple relational calculus
Domain relational calculus
Pure languages form underlying basis of query languages that people use.
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Relational AlgebraRelational Algebra
Procedural language
Six basic operators
select: project: union: set difference: –
Cartesian product: x
rename: The operators take one or two relations as inputs and produce a new
relation as a result.
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Select Operation – ExampleSelect Operation – Example
Relation rA B C D
1
5
12
23
7
7
3
10
A=B ^ D > 5 (r)A B C D
1
23
7
10
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Project Operation – ExampleProject Operation – Example
Relation r: A B C
10
20
30
40
1
1
1
2
A C
1
1
1
2
=
A C
1
1
2
A,C (r)
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Union Operation – ExampleUnion Operation – Example
Relations r, s:
r s:
A B
1
2
1
A B
2
3
rs
A B
1
2
1
3
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Set Difference Operation – ExampleSet Difference Operation – Example
Relations r, s:
r – s:
A B
1
2
1
A B
2
3
rs
A B
1
1
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Cartesian-Product Operation – ExampleCartesian-Product Operation – Example
Relations r, s:
r x s:
A B
1
2
A B
11112222
C D
1010201010102010
E
aabbaabb
C D
10102010
E
aabbr
s
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Rename OperationRename Operation
Allows us to name, and therefore to refer to, the results of relational-algebra expressions.
Allows us to refer to a relation by more than one name.
Example:
x (E)
returns the expression E under the name X
If a relational-algebra expression E has arity n, then
returns the result of expression E under the name X, and with the
attributes renamed to A1 , A2 , …., An .
)(),...,,( 21E
nAAAx
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Composition of OperationsComposition of Operations Can build expressions using multiple operations
Example: A=C(r x s)
r x s
A=C(r x s)
A B
11112222
C D
1010201010102010
E
aabbaabb
A B C D E
122
101020
aab
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Banking ExampleBanking Example
branch (branch_name, branch_city, assets)
customer (customer_name, customer_street, customer_city)
account (account_number, branch_name, balance)
loan (loan_number, branch_name, amount)
depositor (customer_name, account_number)
borrower (customer_name, loan_number)
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Example QueriesExample Queries
Find all loans of over $1200
Find the loan number for each loan of an amount greater than $1200
amount > 1200 (loan)
loan_number (amount > 1200 (loan))
Find the names of all customers who have a loan, an account, or both, from the bank
customer_name (borrower) customer_name (depositor)
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Example QueriesExample Queries
Find the names of all customers who have a loan at the Perryridge branch.
Find the names of all customers who have a loan at the Perryridge branch but do not have an account at any branch of the bank.
customer_name (branch_name = “Perryridge”
(borrower.loan_number = loan.loan_number(borrower x loan))) –
customer_name(depositor)
customer_name (branch_name=“Perryridge”
(borrower.loan_number = loan.loan_number(borrower x loan)))
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Example QueriesExample Queries
Find the names of all customers who have a loan at the Perryridge branch.
customer_name(loan.loan_number = borrower.loan_number (
(branch_name = “Perryridge” (loan)) x borrower))
customer_name (branch_name = “Perryridge” (
borrower.loan_number = loan.loan_number (borrower x loan)))
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Additional OperationsAdditional Operations
Additional Operations
Set intersection
Natural join
Aggregation
Outer Join
Division
All above, other than aggregation, can be expressed using basic operations we have seen earlier
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Set-Intersection Operation – ExampleSet-Intersection Operation – Example
Relation r, s:
r s
A B
121
A B
23
r s
A B
2
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Natural Join Operation – ExampleNatural Join Operation – Example
Relations r, s:
A B
12412
C D
aabab
B
13123
D
aaabb
E
r
A B
11112
C D
aaaab
E
s
r s
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Notation: r s
Natural-Join OperationNatural-Join Operation
Let r and s be relations on schemas R and S respectively. Then, r s is a relation on schema R S obtained as follows:
Consider each pair of tuples tr from r and ts from s.
If tr and ts have the same value on each of the attributes in R S, add a
tuple t to the result, where
t has the same value as tr on r
t has the same value as ts on s
Example:
R = (A, B, C, D)
S = (E, B, D)
Result schema = (A, B, C, D, E)
r s is defined as:
r.A, r.B, r.C, r.D, s.E (r.B = s.B r.D = s.D (r x s))
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Aggregate Functions and OperationsAggregate Functions and Operations
Aggregation function takes a collection of values and returns a single value as a result.
avg: average valuemin: minimum valuemax: maximum valuesum: sum of valuescount: number of values
Aggregate operation in relational algebra
E is any relational-algebra expression
G1, G2 …, Gn is a list of attributes on which to group (can be empty)
Each Fi is an aggregate function
Each Ai is an attribute name
)()(,,(),(,,, 221121E
nnn AFAFAFGGG
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Aggregate Operation – ExampleAggregate Operation – Example
Relation r:
A B
C
7
7
3
10
g sum(c) (r) sum(c )
27
Question: Which aggregate operations cannot be expressed using basic relational operations?
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Aggregate Operation – ExampleAggregate Operation – Example
Relation account grouped by branch-name:
branch_name g sum(balance) (account)
branch_name account_number balance
PerryridgePerryridgeBrightonBrightonRedwood
A-102A-201A-217A-215A-222
400900750750700
branch_name sum(balance)
PerryridgeBrightonRedwood
13001500700
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Aggregate Functions (Cont.)Aggregate Functions (Cont.)
Result of aggregation does not have a name
Can use rename operation to give it a name
For convenience, we permit renaming as part of aggregate operation
branch_name g sum(balance) as sum_balance (account)
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Outer JoinOuter Join
An extension of the join operation that avoids loss of information.
Computes the join and then adds tuples form one relation that does not match tuples in the other relation to the result of the join.
Uses null values:
null signifies that the value is unknown or does not exist
All comparisons involving null are (roughly speaking) false by definition.
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Outer Join – ExampleOuter Join – Example
Relation loan
Relation borrower
customer_name loan_number
JonesSmithHayes
L-170L-230L-155
300040001700
loan_number amount
L-170L-230L-260
branch_name
DowntownRedwoodPerryridge
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Outer Join – ExampleOuter Join – Example
Join
loan borrower
loan_number amount
L-170L-230
30004000
customer_name
JonesSmith
branch_name
DowntownRedwood
JonesSmithnull
loan_number amount
L-170L-230L-260
300040001700
customer_namebranch_name
DowntownRedwoodPerryridge
Left Outer Join
loan borrower
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Outer Join – ExampleOuter Join – Example
loan_number amount
L-170L-230L-155
30004000null
customer_name
JonesSmithHayes
branch_name
DowntownRedwoodnull
loan_number amount
L-170L-230L-260L-155
300040001700null
customer_name
JonesSmithnullHayes
branch_name
DowntownRedwoodPerryridgenull
Full Outer Join
loan borrower
Right Outer Join
loan borrower
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Null ValuesNull Values
It is possible for tuples to have a null value, denoted by null, for some
of their attributes
null signifies an unknown value or that a value does not exist.
The result of any arithmetic expression involving null is null.
Aggregate functions simply ignore null values (as in SQL)
For duplicate elimination and grouping, null is treated like any other
value, and two nulls are assumed to be the same (as in SQL)
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Bank Example QueriesBank Example Queries
Find the names of all customers who have a loan and an account at bank.
customer_name (borrower) customer_name (depositor)
Find the name of all customers who have a loan at the bank and the
loan amount
customer_name, loan_number, amount (borrower loan)
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Query 1
customer_name (branch_name = “Downtown” (depositor account ))
customer_name (branch_name = “Uptown” (depositor account))
Bank Example QueriesBank Example Queries
Find all customers who have an account from at least the “Downtown” and the Uptown” branches.
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ReferenceReference
Silberschatz, Database System Concepts-5th edition