1. MGS 4020 Business Intelligence Relational Algebra and Structured Query Language Jul 3, 2018

2. Agenda
SQL
Queries
Join

3. Set Operations Unary Restriction Projection Binary Union Intersection? ?
Difference
UNION

4. SQL Building Blocks CREATE, ALTER, DROP INSERT, DELETE, UPDATE SELECT
UNION, INTERSECT, MINUS
JOIN
INDEX
VIEWS
Utilities (introduced throughout the examples).
Transaction Management Features
Additional Features

5. Algebra: selection or restriction (R)
Horizontal Slices
Restriction
Specifying Conditions
Algebra: selection
or restriction
(R)
Unconditional
List all students
select *
from STUDENT;
(Student)
Conditional
List all student with GPA > 3.0
select *
from STUDENT
where GPA > 3.0;
GPA > 3.0 (Student)

6. where course# like CIS%’;
Pattern Matching
‘%’ any string with n characters, n>=0
‘_’ any single character.
x exact sequence of string x.
List all CIS courses.
select *
from COURSE
where course# like CIS%’;
List all CIS 3200 levelcourses.
select *
from COURSE
where course# like ? ;

7. Specifying Conditions
List all students in ...
select *
from STUDENT
where city in (‘Boston’,’Atlanta’);
List all students in ...
select *
from STUDENT
where zip not between and 60123;

8. Algebra: projection <A1,A2,...Am> (R) Vertical Slices
Specifying Elements
Algebra: projection
<A1,A2,...Am> (R)
No Specification
List all information about Students
select *
from STUDENT;
(Student)
Conditional
List IDs, names, and addresses of all students
select ID, name, address
from STUDENT;
ID, name, address (Student)

9. Does SQL treat Relations as ‘Sets’
What are the different salaries we pay to our employees?
select salary
from EMPLOYEE;
OR is the following better?
select DISTINCT salary
Is the following necessary?

10. Horizontal and Vertical
Query:
Lista all student ID, names and addresses who have
GPA > 3.0 and age >20.
select ID, Name, Address
from STUDENT
where GPA > 3.0 and DOB < ‘1-Jan-6’
order by Name DESC;
Algebra:
ID,name, address ( GPA > 3.0 and DOB < ‘1-Jan-74’ (STUDENT)
Order by sorts result in descending (DESC) order.
Note: The defauld order is ascending (ASC) as in:
order by Name;

11. Agenda
SQL
Queries
Join

12. Relational Database
A relational database is a collection of data items organized as a set of formally-described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables. The relational database was invented by E. F. Codd at IBM in 1970.
The standard user and application program interface to a relational database is the structured query language (SQL). SQL statements are used both for interactive queries for information from a relational database and for gathering data for reports.
A relational database is a set of tables containing data fitted into predefined categories. Each table (which is sometimes called a relation) contains one or more data categories in columns. Each row contains a unique instance of data for the categories defined by the columns. For example, a typical business order entry database would include a table that described a customer with columns for name, address, phone number, and so forth. Another table would describe an order: product, customer, date, sales price, and so forth. A user of the database could obtain a view of the database that fitted the user's needs. For example, a branch office manager might like a view or report on all customers that had bought products after a certain date. A financial services manager in the same company could, from the same tables, obtain a report on accounts that needed to be paid.

13. Relational Database
When creating a relational database, you can define the domain of possible values in a data column and further constraints that may apply to that data value. For example, a domain of possible customers could allow up to ten possible customer names but be constrained in one table to allowing only three of these customer names to be specifiable.
The definition of a relational database results in a table of metadata or formal descriptions of
the tables, columns, domains, and constraints. Meta is a prefix that in most information technology usages means "an underlying definition or description." Thus, metadata is a definition or description of data and metalanguage is a definition or description of language.
A database is a collection of data that is organized so that its contents can easily be accessed, managed, and updated. The most prevalent type of database is the relational database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network. An object-oriented programming database is one that is congruent with the data defined in object classes and subclasses.
SQL (Structured Query Language) is a standard interactive and programming language for getting information from and updating a database. Although SQL is both an ANSI and an ISO standard, many database products support SQL with proprietary extensions to the standard language. Queries take the form of a command language that lets you select, insert, update, find out the location of data, and so forth.

14. Nesting Queries SELECT attribute(s) FROM relation(S)
WHERE attr [not] {in | comparison operator | exists }
( query statement(s) );
List names of students who are taking “BA201”
select Name
from Student
where ID in
( select ID
from REGISTRATION
where course#=‘BA201’);

15. Sub Queries List all students enrolled in CIS courses select name
from STUDENT
where studentnum in
(select StudentId
from REGISTRATION
where cno like ‘CIS%’);
List all courses taken by Student (Id 1011)
select cname
from COURSE
where cnum _ any
(select cno
from REGISTRATION
where StudentId = 1011);

16. Sub Queries Who received the highies grade in CIS 814 select StudentId
from GRADE
where cnum = ‘CIS 814’ and
grade >=all
(select grade
where cno = ‘CIS 814’);
List all students enrolled in CIS courses.
select name
from STUDENT S
where exists
(select *
from REGISTRATION
where StudentId = S.Studentnum
and cno like “CIS%’);

17. Recursive Queries List all employees who earn more than their
immediate supervisor.
select E.Emp#, E.title, E.salary
from EMPLOYEE, EMPLOYEE M
where E.salary > M.salary and
E.ManagerEmp# = M.Wmp#;

18. Summaries and Aggregates
Calculate the average GPA select avg. (GPA)
from STUDENT,
Find the lowest GPA select min (GPA) as minGPA
How many CIS majors? select count (StudentId)
from STUDENT
where major=‘CIS’;
Discarding duplicates select avg (distinct GPA)
where major=‘CIS’

19. Aggregate Functions COUNT (attr) - a simple count of values in attr
SUM (attr) - sum of values in attr
AVG (attr) - average of values in attr
MAX (attr) - macimum value in attr
MIN (attr) - minimum value in attr
Take effect after data are retrieved from the database
Applied to either the entire resulting relation or groups
Can’t be involved in any query qualifications (where clause)
Would the following query be permitted?
select StudentId
from STUDENT
where GPA = max (GPA);

20. Missing or Incomplete Information
List all students whose address or telephone number is missing:
select *
from STUDENT
where Address is null or GPA is null;
Truth Table T T T F F F U U U
T F U T F U T F U
~ a
a & b
a or b

21. Groupin Results Obtained
Show all students enrolled in each course.
select cno, stno
from REGISTRATION
group by cno; Is this grouping OK?
Calculate the average GPA of students by county.
select county, avg (GPA) as County GPA
from STUDENT
group by county;
Calculate the average GPA of each class.
select cno, term, year, count (stno) as enrol
group by cno, year, term;

22. Selections on Groups Show all CIS courses that are full.
select cno, count (stno)
from REGISTRATION
group by cno
having count (stno) > 29;

23. Union List students who live in Atlanta or GPA > 3.0
select ID, Name, DOB, Address
from STUDENT
where Address = ‘Atlanta’
union
where GPA > 3.0;
Can we perform a Union on any two Relations ?

24. Union Compatibility Two relations, A and B, are union-compatible if
1) A and B contain a same number of attributes, and
2) The corresponding attributes of the two have the same domains
Examples
CIS=Student (ID: Did; Name: Dname; Address: Daddr; Grade: Dgrade);
Senior-Student (SName: Dname; S#: Did; Home: Daddr; Grade: Dgrade);
Course (C#: Dnumber; Title: Dstr; Credits: Dnumber)
Are CIS-Student and Senior-Student union compatible?
Are CIS-Student and Couse union compatible?
What happens if we have duplicate tuples?
What will be the column names in the resulting Relation?

25. Union, Intersect, Minus select CUSTNAME, ZIP select CUSTNAME, ZIP
from CUSTOMER
where STATE = ‘MA’
UNION
select SUPNAME, ZIP
from SUPPLIER
where STATE = ‘MA’
ORDER BY 2;
select CUSTNAME, ZIP
from CUSTOMER
where STATE = ‘MA’
INTERSECT
select SUPNAME, ZIP
from SUPPLIER
where STATE = ‘MA’
ORDER BY 2;
select CUSTNAME, ZIP
from CUSTOMER
where STATE = ‘MA’
MINUS
select SUPNAME, ZIP
from SUPPLIER
where STATE = ‘MA’
ORDER BY 2; B B A A A B A

26. Union, Intersect, Minus

27. Agenda
SQL
Queries
Join

28. Connecting/Linking Relations
List information about all students and the classes they are taking
Student
Class
What can we use to connect/link Relations?
Join: Connecting relations so that relevant tuples can be retrieved.

29. Total Number of Tuples in the Cartesian Product. ?
Join
Cartesian
Product R1 R2
Student: 30 tuples
Class: 4 tuples
Total Number of Tuples in the Cartesian Product. ?
(match each tuple of student to every tuple of class)
Select tuples having identical Student Ids.
Expected number of such Tuples: Join Selectivity

30. = x > y <> ... Join Forms R1 R2 select s.*.c.*
General Join Forms
Equijoin
Operator Dependent
Natural Join
Outer Join
Left
Right
Full
select s.*.c.*
from STUDENT s, CLASS c
where s.ID = c. ID; R1 R2 =
x > y
<>
...
select s.*.c.*
from STUDENT s, CLASS c
where s.ID = c. ID (+);

31. Grouping Results after Join
Calculate the average GPA of each class
select course#, avg (GPA)
from STUDENT S, CLASS C
where S.ID = C.ID
group by course#,

32. Index There is no order among tuples Indexes speed up data retrieval
Find all students who live in Atlanta.
How many tuples would you have to search for this query?
What if the table was ‘indexed’?
Index Table Student

33. Creating and Deleting Indices
CREATE [UNIQUE] INDEX index name
ON base-relation-name
( attr-name [order], attr-name[order] ...)
[CLUSTER];
create unique index student-id
on STUDENT ( ID ASC );
create index Address-index
on Student (Address);
create unique index Name-Age-Index
on STUDENT ( Name DESC, Age );
What are the advantages & disadvantages of Indexing?

34. View 1 View 2 View N Base Relation 1 Relation 2 Relational Views
Relations derived from other relations.
Views have no stored tuples.
Are useful to provide multiple user views.
View 1
View 2
View N
Base
Relation 1
Relation 2

35. View Creation Create View view-name [ ( attr [ , attr ] ...) ]
AS subquery
[ with check option ] ;
DROP VIEW view-name;
Create a view containing the student ID, Name, Age and GPA for those who are qualified to take 300 level courses, i.e., GPA >=2.0.

36. View Options
With Check Option enforces the query condition for insertion or update
To enforce the GPA >=2.0 condition on all new student tuples inserted into the view
A view may be derived from multiple base relations
Create a view that includes student IDs, student names and their instructors’ names for all CIS 300 students.

37. View Retrieval
Queries on views are the same as that on base relations.
Queries on views are expanded into queries on their base relations.
select Name, Instructor-Name
from CIS300-Student
where Name = Instructor-Name; ?

38. View: Update Update on a view actually changes its base relation(s)!
update Qualified-Student
set GPA = GPA-0.1
where SID = ‘s3’;
insert into Qualified-Student
values ( ‘s9’, ‘Lisa’, 4.0 )
values ( ‘s10’, ‘Peter’, 1.7 )
Why are some views not updateable?
What type of views are updateable?