Summary: Databases, 2018-2019
Bibliography
Week 1: Chapter 1 ............................................................................................................................. 4
Introduction, motivation, data representation and DBMS ............................................................................ 4
Week 2: Chapter 3.1, 3.2, 3.3, 3.4, 3.7, 3.9 .......................................................................................... 9
Chapter 4.1, 4.2, 4.4, 4.5 ............................................................................................................................. 9
SQL ............................................................................................................................................................ 9
3.1 Overview of the SQL language ....................................................................................................................... 9
3.2 SQL data definition......................................................................................................................................... 9
3.3 Basic structures of SQL queries .................................................................................................................... 11
The natural join ............................................................................................................................................. 13
3.4 Additional basic operations ......................................................................................................................... 13
String operators ............................................................................................................................................ 13
3.7 Aggregate functions..................................................................................................................................... 14
The having clause .......................................................................................................................................... 14
4.1 Join expressions............................................................................................................................................ 16
Join conditions .............................................................................................................................................. 16
Outer joins ..................................................................................................................................................... 16
4.2 Views ............................................................................................................................................................ 16
View definition .............................................................................................................................................. 16
Materialised views ........................................................................................................................................ 17
Update of a view ........................................................................................................................................... 17
4.4 Integrity constraints ..................................................................................................................................... 17
Constraints on a single relation .................................................................................................................... 17
Not null constraint ........................................................................................................................................ 17
Unique constraint ......................................................................................................................................... 18
The check clause ........................................................................................................................................... 18
Referential integrity ...................................................................................................................................... 18
Integrity constraints violation during a transaction ..................................................................................... 18
Complex check conditions and assertions .................................................................................................... 18
1
, 4.5 SQL data types and schemas ....................................................................................................................... 19
Default values................................................................................................................................................ 19
User-defined types ........................................................................................................................................ 19
Week 3: Chapter 7.1, 7.2, 7.5 ................................................................................................................ 20
Conceptual data modelling: The ER model ................................................................................................. 20
7.1 Overview of the design process ................................................................................................................... 20
7.2 The entity-relationship model ...................................................................................................................... 21
7.5 Entity-relationship diagrams........................................................................................................................ 22
Mapping cardinality ...................................................................................................................................... 23
Complex constraints...................................................................................................................................... 23
Complex attributes........................................................................................................................................ 24
Nonbinary relationship sets .......................................................................................................................... 24
Weak entity sets............................................................................................................................................ 24
A complete ER diagram ................................................................................................................................. 25
Week 4: Chapter 7.7, 7.6, 7.8: ER diagrams, relational schema and advanced SQL .............................. 26
7.6 Reduction to relational schemas.................................................................................................................. 26
Representation of strong entity sets with simple attributes ........................................................................ 26
Representation of strong entity sets with complex attributes ..................................................................... 26
Representation of weak entity sets .............................................................................................................. 26
Representation of relationship sets .............................................................................................................. 27
Redundancy of schemas ............................................................................................................................... 27
7.7 Use of entity sets versus attributes .............................................................................................................. 27
Use of entity sets versus relationship sets.................................................................................................... 27
Placement of relationship attributes ............................................................................................................ 28
7.8 Extended E-R features .................................................................................................................................. 28
Week 5: Chapter 8.1, 8.2, 8.3.1, 8.4.1, 8.4.2, 8.4.3.................................................................................. 30
Database Design Theory I: Functional dependencies and normalisation ...................................................... 30
8.1 Features of good relational designs ............................................................................................................. 30
8.2 Atomic domains and first normal form ........................................................................................................ 30
8.3 Decomposition using functional dependencies............................................................................................ 30
Keys and functional dependencies ............................................................................................................... 30
8.4 Functional-dependency theory .................................................................................................................... 31
2
, Closure of a set of functional dependencies ................................................................................................ 31
Canonical cover ............................................................................................................................................. 32
Week 6: Chapter 8.3 ............................................................................................................................. 34
Database Design Theory II: Functional dependencies and normalisation ..................................................... 34
8.3 Decomposition using functional dependencies............................................................................................ 34
Boyce-Codd normal form .............................................................................................................................. 34
Third normal form ......................................................................................................................................... 34
Task list for normalisation of databases..................................................................................................... 35
Rough outline of the steps needed: ................................................................................................................... 35
3
, Week 1: Chapter 1
Introduction, motivation, data representation and DBMS
A database-management system (DBMS) consists of a collection of interrelated data and a
collection of programs to access that data. The data describe one particular enterprise.
The primary goal of a DBMS is to provide an environment that is both convenient and
efficient for people to use in retrieving and storing information.
Database systems are ubiquitous today, and most people interact, either directly or
indirectly, with databases many times every day.
The file-processing system was widely used before but has some major disadvantages:
• Data redundancy and inconsistency;
• Difficulty in accessing data;
• Data isolation;
• Integrity problems;
• Atomicity problems;
• Concurrent-access anomalies;
• Security problems.
Database systems are designed to store large bodies of information. The management
of data involves both the definition of structures for the storage of information and the provision
of mechanisms for the manipulation of information. In addition, the database system must
provide for the safety of the information stored, in the face of system crashes or attempts at
unauthorized access. If data are to be shared among several users, the system must avoid
possible anomalous results.
A major purpose of a databases system is to provide users with an abstract view of the
data. That is, the system hides certain details of how the data are stored and maintained. There
are three levels of abstraction:
• Physical level:
o The lowest level of abstraction describes how the data are actually stored.
This level describes complex low-level data structures in detail
• Logical level:
o The next-higher level describes what data are stored in the database, and
what relationships exist among those data. It describes the total database
in a number of small relatively simple structures. Although the
4
Bibliography
Week 1: Chapter 1 ............................................................................................................................. 4
Introduction, motivation, data representation and DBMS ............................................................................ 4
Week 2: Chapter 3.1, 3.2, 3.3, 3.4, 3.7, 3.9 .......................................................................................... 9
Chapter 4.1, 4.2, 4.4, 4.5 ............................................................................................................................. 9
SQL ............................................................................................................................................................ 9
3.1 Overview of the SQL language ....................................................................................................................... 9
3.2 SQL data definition......................................................................................................................................... 9
3.3 Basic structures of SQL queries .................................................................................................................... 11
The natural join ............................................................................................................................................. 13
3.4 Additional basic operations ......................................................................................................................... 13
String operators ............................................................................................................................................ 13
3.7 Aggregate functions..................................................................................................................................... 14
The having clause .......................................................................................................................................... 14
4.1 Join expressions............................................................................................................................................ 16
Join conditions .............................................................................................................................................. 16
Outer joins ..................................................................................................................................................... 16
4.2 Views ............................................................................................................................................................ 16
View definition .............................................................................................................................................. 16
Materialised views ........................................................................................................................................ 17
Update of a view ........................................................................................................................................... 17
4.4 Integrity constraints ..................................................................................................................................... 17
Constraints on a single relation .................................................................................................................... 17
Not null constraint ........................................................................................................................................ 17
Unique constraint ......................................................................................................................................... 18
The check clause ........................................................................................................................................... 18
Referential integrity ...................................................................................................................................... 18
Integrity constraints violation during a transaction ..................................................................................... 18
Complex check conditions and assertions .................................................................................................... 18
1
, 4.5 SQL data types and schemas ....................................................................................................................... 19
Default values................................................................................................................................................ 19
User-defined types ........................................................................................................................................ 19
Week 3: Chapter 7.1, 7.2, 7.5 ................................................................................................................ 20
Conceptual data modelling: The ER model ................................................................................................. 20
7.1 Overview of the design process ................................................................................................................... 20
7.2 The entity-relationship model ...................................................................................................................... 21
7.5 Entity-relationship diagrams........................................................................................................................ 22
Mapping cardinality ...................................................................................................................................... 23
Complex constraints...................................................................................................................................... 23
Complex attributes........................................................................................................................................ 24
Nonbinary relationship sets .......................................................................................................................... 24
Weak entity sets............................................................................................................................................ 24
A complete ER diagram ................................................................................................................................. 25
Week 4: Chapter 7.7, 7.6, 7.8: ER diagrams, relational schema and advanced SQL .............................. 26
7.6 Reduction to relational schemas.................................................................................................................. 26
Representation of strong entity sets with simple attributes ........................................................................ 26
Representation of strong entity sets with complex attributes ..................................................................... 26
Representation of weak entity sets .............................................................................................................. 26
Representation of relationship sets .............................................................................................................. 27
Redundancy of schemas ............................................................................................................................... 27
7.7 Use of entity sets versus attributes .............................................................................................................. 27
Use of entity sets versus relationship sets.................................................................................................... 27
Placement of relationship attributes ............................................................................................................ 28
7.8 Extended E-R features .................................................................................................................................. 28
Week 5: Chapter 8.1, 8.2, 8.3.1, 8.4.1, 8.4.2, 8.4.3.................................................................................. 30
Database Design Theory I: Functional dependencies and normalisation ...................................................... 30
8.1 Features of good relational designs ............................................................................................................. 30
8.2 Atomic domains and first normal form ........................................................................................................ 30
8.3 Decomposition using functional dependencies............................................................................................ 30
Keys and functional dependencies ............................................................................................................... 30
8.4 Functional-dependency theory .................................................................................................................... 31
2
, Closure of a set of functional dependencies ................................................................................................ 31
Canonical cover ............................................................................................................................................. 32
Week 6: Chapter 8.3 ............................................................................................................................. 34
Database Design Theory II: Functional dependencies and normalisation ..................................................... 34
8.3 Decomposition using functional dependencies............................................................................................ 34
Boyce-Codd normal form .............................................................................................................................. 34
Third normal form ......................................................................................................................................... 34
Task list for normalisation of databases..................................................................................................... 35
Rough outline of the steps needed: ................................................................................................................... 35
3
, Week 1: Chapter 1
Introduction, motivation, data representation and DBMS
A database-management system (DBMS) consists of a collection of interrelated data and a
collection of programs to access that data. The data describe one particular enterprise.
The primary goal of a DBMS is to provide an environment that is both convenient and
efficient for people to use in retrieving and storing information.
Database systems are ubiquitous today, and most people interact, either directly or
indirectly, with databases many times every day.
The file-processing system was widely used before but has some major disadvantages:
• Data redundancy and inconsistency;
• Difficulty in accessing data;
• Data isolation;
• Integrity problems;
• Atomicity problems;
• Concurrent-access anomalies;
• Security problems.
Database systems are designed to store large bodies of information. The management
of data involves both the definition of structures for the storage of information and the provision
of mechanisms for the manipulation of information. In addition, the database system must
provide for the safety of the information stored, in the face of system crashes or attempts at
unauthorized access. If data are to be shared among several users, the system must avoid
possible anomalous results.
A major purpose of a databases system is to provide users with an abstract view of the
data. That is, the system hides certain details of how the data are stored and maintained. There
are three levels of abstraction:
• Physical level:
o The lowest level of abstraction describes how the data are actually stored.
This level describes complex low-level data structures in detail
• Logical level:
o The next-higher level describes what data are stored in the database, and
what relationships exist among those data. It describes the total database
in a number of small relatively simple structures. Although the
4
