Learn Relational Database from Scratch. Dan Li, Ph.D. Associate Professor Computer Science Eastern Washington University

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1 Learn Relational Database from Scratch Dan Li, Ph.D. Associate Professor Computer Science Eastern Washington University

2 Self-Introduction Associate professor of Computer Science at EWU Area of expertise Databases Relational database systems Advanced database management systems Modern database systems Data analysis Data mining Big data analytics Free feel to talk to me if you are interest in our graduate program Contact 2

3 Objectives Target audience: no relational database background Understand a DBMS (DataBase Management System) and its architecture Distinguish between different database models Understand the concept of relational database Use SQL (Structured Query Language) to define and query simple relations 3

4 DBMS Database: a large collection of data that are logically related DBMS: a software package designed to store and manage databases Three-level architecture 4

5 External Level Interacts directly with the user Collects data from a format that is familiar to the user 5

6 Conceptual Level Defines the logical view of the data Main functions of DBMS are in this level 6

7 Internal Level Determines where and how data are actually stored on the physical storage device 7

8 Database Models A database model Defines the logical (conceptual) design of data Describes the relationships between different parts of data 3 models Hierarchical model Network model Relational model 8

9 Hierarchical Model Data are organized as an upside down tree Each entity has only one parent but can have several children 9

10 Network Model The entities are organized as a graph Some entities can be accessed through several paths 10

11 Relational Model Data are organized as two-dimensional tables called relations The tables are related to each other The most popular model 11

12 Relation Name each relation in a relational database should have a name that is unique among other relations. Attribute each column in a relation. The degree of the relation the total number of attributes for a relation. Tuple each row in a relation. The cardinality of the relation the total number of rows in a relation. 12

13 Create a New Relation using SQL SQL: Structured Query Language Standardized by ANSI and ISO for use on relational databases. It is a declarative (not procedural) language, which means that the users declare what they want without having to write a step-bystep procedure. SQL allows to create new relations and extract more complex information from existing relations. Create Table COURSES( No char(5) primary key, Course-Name varchar(64), Unit integer); 13

14 Operations on Relations In a relational database, we can define several operations to create new relations out of existing relations or update existing ones. Basic operations Select Project Join Union Intersection Difference Insertion Deletion Update 14

15 SELECT Operation An unary operation. It is applied to one single relation and creates another relation. The tuples in the resulting relation are a subset of the tuples in the original relation. Use some criteria to select, e.g. Unit = 5 15

16 SELECT Operation in SQL select * from RELATION-NAME where criteria select * from COURSES where Unit=5 16

17 PROJECT Operation An unary operation. It is applied to one single relation and creates another relation. The attributes in the resulting relation are a subset of the attributes in the original relation. 17

18 PROJECT Operation in SQL select attribute-list from RELATION-NAME select No, Unit from COURSES 18

19 JOIN Operation A binary operation. Combines two relations based on join conditions. 19

20 JOIN Operation in SQL select attribute-list from RELATION1,RELATION2 where join-condition select No,Course-Name,Unit,Professor from COURSES,TAUGHT-BY where COURSES.No=TAUGHT-BY.No 20

21 JOIN Operation in SQL (cont d) select attribute-list from RELATION1 join RELATION2 using (common-attribute-list) select No,Course-Name,Unit,Professor from COURSES join TAUGHT-BY using (No) 21

22 UNION Operation A binary operation. Creates a new relation in which each tuple is either in the first relation, in the second, or in both. The two relations must have the same or comparable attributes. 22

23 UNION Operation in SQL select * from RELATION1 union select * from RELATION2 select * from CIS15-Roster union select * from CIS52-Roster 23

24 INTERSECTION Operation A binary operation. Creates a new relation in which each tuple is a member in both relations. The two relations must have the same or comparable attributes. 24

25 INTERSECTION Operation in SQL select * from RELATION1 intersect select * from RELATION2 select * from CIS15-Roster intersect select * from CIS52-Roster 25

26 DIFFERENCE Operation A binary operation. Creates a new relation in which each tuple is in the first relation but not the second. The two relations must have the same or comparable attributes. 26

27 DIFFERENCE Operation in SQL select * from RELATION1 except select * from RELATION2 select * from CIS15-Roster except select * from CIS52-Roster 27

28 INSERTION Operation An unary operation. Insert a new tuple into an existing relation. 28

29 INSERTION Operation in SQL insert into RELATION-NAME values (,, ) insert into COURSES values ( CIS52, TCP/IP, 6 ) 29

30 DELETION Operation An unary operation. Delete existing tuples defined by a criterion from the relation. 30

31 DELETION Operation in SQL delete from RELATION-NAME where criteria delete from COURSES where No= CIS19 31

32 UPDATE Operation An unary operation. Changes the value of some attributes of a tuple. 32

33 UPDATE Operation in SQL update RELATION-NAME set attribute1=value1, attribute2=value2, where criteria update COURSES set Unit=6 where No= CIS51 33

34 Let s Go A Little Further Remember that a relational operation generates a new relation. This new relation can be further used as input for the next operation. select No, Course-Name from COURSES where Unit=5 34

35 Objectives Revisited Understand a DBMS (DataBase Management System) and its architecture Distinguish between different database models Understand the concept of relational database Use SQL (Structured Query Language) to define and query simple relations 35