SQL logical operators

Department of Information Technology 1Data base Technologies (ITB4201)
Structured Query Language
Logical Operators
Dr. C.V. Suresh Babu
Professor
Department of IT
Hindustan Institute of Science & Technology

Action Plan
• Logical Operators
• LISTS (IN AND NOT IN)
• RANGES (BETWEEN AND NOT BETWEEN)
• ORDER BY
• Aggregate functions
• GROUP BY and HAVING
• UNION

LOGICAL OPERATORS
(AND, OR, AND NOT)
• AND : Joins two or more conditions, and returns results only
when all of the conditions are true.
• OR : Joins two or more conditions, and returns results when any
of the conditions are true.
• NOT : Negates the expression that follows it.

AND OPERATOR
SELECT emp_last_name "Last Name",
emp_first_name "First Name",
emp_gender "Gender"
FROM employee
WHERE emp_gender = 'F' AND emp_last_name > ‘E'
ORDER BY emp_last_name;
Last Name First Name Gender
---------- ------------- ------
Joyner Suzanne F
Markis Marcia F
Prescott Sherri F

OR OPERATOR
emp_gender "Gender"
FROM employee
WHERE emp_gender = 'F' OR emp_last_name > 'M'
Last Name First Name Gender
--------------- --------------- ------
Joyner Suzanne F
Markis Marcia F
Prescott Sherri F
Zhu Waiman M

NOT OPERATOR
emp_dpt_number "Dept"
FROM employee
WHERE NOT emp_dpt_number = 7
Last Name First Name Dept
--------------- --------------- -----
Amin Hyder 3
Bordoloi Bijoy 1
Joyner Suzanne 3
Markis Marcia 3

Combining OR and AND Operators
• When the AND operator is combined with OR,
the Oracle server will evaluate the condition
connected by the AND first before any
conditions connected with OR.
• Parenthesis must be used to force an order of
operation.

emp_dpt_number "Dept", emp_gender "Gender"
FROM employee
WHERE emp_last_name > 'E' AND emp_gender = 'F‘
OR emp_dpt_number = 1
Last Name First Name Dept Gender
--------------- -------------- ----- ------
Bordoloi Bijoy 1 M
Joyner Suzanne 3 F
Markis Marcia 3 F
Prescott Sherri 7 F

emp_dpt_number "Dept", emp_gender "Gender"
FROM employee
WHERE emp_last_name > 'E' AND
(emp_gender = 'F' OR emp_dpt_number = 1)
Last Name First Name Dept Gender
--------------- --------------- ----- ------
Joyner Suzanne 3 F
Markis Marcia 3 F
Prescott Sherri 7 F

LISTS (IN AND NOT IN)
• There are two operators that are designed for testing to determine if data stored
in a table column is either in or not in a list or set of values.
• These are the IN and NOT IN operators.
• These operators greatly simplify the task of writing queries that might otherwise
require a large number of either OR logical operators or an unwieldy use of the
NOT logical operator.

Using IN Operator
SELECT emp_last_name "Last Name", emp_first_name "First
Name",
emp_salary "Salary"
FROM employee
WHERE emp_salary = 43000 OR emp_salary = 30000 OR
emp_salary = 25000
ORDER BY emp_salary;
Last Name First Name Salary
--------------- --------------- -----------
Markis Marcia $25,000.00
Amin Hyder $25,000.00
Prescott Sherri $25,000.00
Bock Douglas $30,000.00
Joyner Suzanne $43,000.00
Zhu Waiman $43,000.00
6 rows selected.

Using IN Operator
SELECT emp_last_name "Last Name", emp_first_name "First Name",
emp_salary "Salary"
FROM employee
WHERE emp_salary IN (43000, 30000, 25000)
--------------- --------------- -----------
6 rows selected.

Using IN Operator
Name",
emp_city "City"
FROM employee
WHERE emp_city IN ('Marina', 'Edwardsville', 'St. Louis')
ORDER BY emp_city;
Last Name First Name City
--------------- --------------- -------------
Bordoloi Bijoy Edwardsville
Prescott Sherri Edwardsville
Joyner Suzanne Marina
Amin Hyder Marina
Zhu Waiman St. Louis
Bock Douglas St. Louis

Using the NOT IN Operator
• NOT can precede IN to form negative.
• To get the list of employees who did not earn the
three salary figures listed above
emp_salary "Salary"
FROM employee
WHERE emp_salary NOT IN (43000, 30000, 25000)
--------------- --------------- -----------
Joshi Dinesh $38,000.00
Bordoloi Bijoy $55,000.00

RANGES (BETWEEN AND NOT BETWEEN)
• SQL provides two operators, BETWEEN and NOT BETWEEN that
can simply the range of values in a query.
• This eliminates the need to use a more complex WHERE clause
involving the use of the AND logical operator.

Using the BETWEEN Operator
• The following query uses the AND logical operator.
emp_salary "Salary"
FROM employee
WHERE emp_salary >= 25000 AND emp_salary <= 40000
-------------- --------------- -----------

Using the BETWEEN Operator
• The query can be rewritten using the BETWEEN
operator.
emp_salary "Salary"
FROM employee
WHERE emp_salary BETWEEN 25000 AND 40000
--------------- --------------- -----------

Using the NOT BETWEEN Operator
SELECT emp_last_name "Last Name", emp_salary "Salary"
FROM employee
WHERE emp_salary NOT BETWEEN 28000 AND 50000
Last Name Salary
--------------- -----------
Markis $25,000.00
Amin $25,000.00
Prescott $25,000.00
Bordoloi $55,000.00

LIKE AND NOT LIKE
• The LIKE and NOT LIKE operators can be used to
search for data rows containing incomplete or partial
character strings within a data column.
• The next query searches the employee table for
employee names that begin with the characters 'Bo'.
• The search is case-sensitive meaning that 'Bo' is not
equivalent to 'BO'.

LIKE AND NOT LIKE
Name"
FROM employee
WHERE emp_last_name LIKE 'Bo%';
Last Name First Name
------------- -------------
Bordoloi Bijoy
Bock Douglas

LIKE AND NOT LIKE
Wild card Meaning
% (percent)any string of zero or more characters
_ (underscore) any single character
[ ] (brackets) any single character within a specified range such as 'a' to 'd', inclusive [a-d]
or a set of characters such as [aeiouy]
[^] (not brackets) any single character not in the specified range or set.(e.g., [^a-f] )
Oracle supports only the first two,
SQL Server and Sybase supports all four.

MORE EXAMPLES
• LIKE '%inger' will search for every name that ends with 'inger' (Ringer,
Stringer).
• LIKE '%en%' will search for every name that has the letters 'en' in the
name (Bennet, Green, McBadden).
• LIKE '_heryl' will search for every six-letter name ending with 'heryl'
(Cheryl). Notice how this is different than '%heryl' which would return
names that are six characters or more.

MORE EXAMPLES
• LIKE '[CK]ars[eo]n' will search for every six-letter name that
begins with a 'C' or 'K' and has the letter 'e' or 'o' between 'ars'
and 'n' (e.g., 'Carsen,' 'Karsen,' 'Carson,' and 'Karson'.
• LIKE '[M-Z]inger' will search for all the names ending with 'inger'
that begin with any single letter 'M' thru 'Z' (Ringer).
• LIKE 'M[^c]%' will search for all the names that begin with 'M'
not having 'c' as the second letter.

MORE EXAMPLES
The SELECT statement shown below generates a result table that includes
all DISTINCT rows where the employee social security number in the
assignment table ends with the numbers 555.
SELECT DISTINCT work_emp_ssn "Emp SSN"
FROM assignment
WHERE work_emp_ssn LIKE '%555';
Emp SSN
------------
999555555

UNKNOWN VALUES
(IS NULL AND IS NOT NULL)
• NULL value is not synonymous with "zero" (numerical values) or "blank"
(character values).
• NULL values allow users to distinguish between a deliberate entry of
zero/blank and a non-entry of data.
SELECT *
FROM assignment
WHERE work_hours IS NULL;
WORK_EMP_ WORK_PRO_NUMBER WORK_HOURS
--------- --------------- ----------
999444444 1
999666666 20

MORE EXAMPLES
SELECT *
FROM assignment
WHERE work_hours = 0;
no rows selected
• The query did not return a result table because none of the rows in the
assignment table have a zero value for work_hours. Thus, you can see
that zero (0) is a value, not an "unknown value."

MORE EXAMPLES
• The NOT NULL condition can also be tested.
SELECT *
FROM assignment
WHERE work_hours IS NOT NULL;
15 rows selected.
• The result table contains all the rows where work_hours column
contains a value.

EXPRESSIONS IN SELECT CLAUSES
• An expression is formed by combining a column name or constant with an
arithmetic operator.
• The arithmetic operators used in SQL are
SYMBOL OPERATION ORDER
* Multiplication 1
/ Division 1
% Modulo 1
+ Addition 2
- Subtraction 2

MORE EXAMPLES
Name",
emp_salary/12 "Monthly Salary"
FROM employee
WHERE emp_salary/12 > 3500
Last Name First Name Monthly Salary
--------------- --------------- --------------
Bordoloi Bijoy $4,583.33

EXPRESSIONS
• When expression is used in select with a column name it has no effect on
the table’s underlying values.
• The data contained in each column must be defined as int, smallint,
tinyint, float, money, and smallmoney.
• The result of an arithmetic operation on NULL is NULL.

Examples of Operations on Nulls
Table: Compensation
EMP# JOBCODE SALARY COMMISSION
E10 SALES 12500 32090
E11 NULL 25000 8000
E12 SALES 44000 0
E13 SALES 44000 NULL
E14 PROG 19500 NULL
E15 CLERK NULL NULL

Examples of Operations on Nulls
List the employees whose total earnings exceed $30000.00.
SELECTEMP#
FROM COMPENSATION
WHERE JOBCODE = “SALES”
AND (SALARY + COMMISSION) > 30000
EMP#
E10
E12
E13 is missing because?

ORDER BY
• The ORDER BY clause sorts the
results of a query
– You can sort in ascending (default) or
descending order
– Multiple columns can be given
– You cannot order by a column which isn’t in
the result
SELECT <columns>
FROM <tables>
WHERE <condition>
ORDER BY <cols>
[ASCENDING |
DESCENDING|
ASC | DESC ]

ORDER BY Example
Grades
Name Code Mark
John DBS 56
John IAI 72
Mary DBS 60
Mark PR1 43
Mark PR2 35
Jane IAI 54
Name Code Mark
Mark PR2 35
Mark PR1 43
Jane IAI 54
John DBS 56
Mary DBS 60
John IAI 72
SELECT * FROM Grades
ORDER BY Mark

ORDER BY Example
Grades
Name Code Mark
John DBS 56
John IAI 72
Mary DBS 60
Mark PR1 43
Mark PR2 35
Jane IAI 54
Name Code Mark
Mary DBS 60
John DBS 56
John IAI 72
Jane IAI 54
Mark PR1 43
Mark PR2 35
SELECT * FROM Grades
ORDER BY Code ASC,
Mark DESC

Constants and Arithmetic
• As well as column names, you can
select constants, compute arithmetic
expressions and evaluate functions in
a SELECT statement
SELECT Mark/100
FROM Grades
SELECT
Salary + Bonus
FROM Employee
SELECT 1.175*Price
FROM Products

Aggregate Functions
• Aggregate functions compute
summaries of data in a table
– Most aggregate functions (all except
COUNT) work on a single column of
numeric data
– Use an alias to name the result
• Aggregate functions
– COUNT: The number of rows
– SUM: The sum of the entries in a column
– AVG: The average entry in a column
– MIN, MAX: The minimum and maximum
entries in a column

Aggregate Functions
Grades
Name Code Mark
John DBS 56
John IAI 72
Mary DBS 60
Mark PR1 43
Mark PR2 35
Jane IAI 54
SELECT
COUNT(*) AS Count
FROM Grades
SELECT
SUM(Mark) AS Total
FROM Grades
SELECT
MAX(Mark) AS Best
FROM Grades
Count
6
Total
320
Best
72

Aggregate Functions
• You can combine aggregate
functions using arithmetic
SELECT
MAX(Mark)-MIN(Mark)
AS Range
FROM Grades
Grades
Name Code Mark
John DBS 56
John IAI 72
Mary DBS 60
Mark PR1 43
Mark PR2 35
Jane IAI 54
Range
37
MAX(Mark) = 72
MIN(Mark) = 35

Example
• Find John’s average mark, weighted by
the credits of each moduleModules
Code Title Credits
DBS Database Sys. 10
GRP Group Project 20
PRG Programming 10
Grades
Name Code Mark
John DBS 60
Mark GRP 47
Mary PRG 56
SELECT
SUM(Mark*Credits)/SUM(Credits)
FROM Modules, Grades
WHERE Modules.Code=Grades.Code
AND Grades.Name = ‘John’

GROUP BY
• Sometimes we want to apply
aggregate functions to groups of rows
• Example, find the average mark of
each student
• The GROUP BY clause does this
SELECT <cols1>
FROM <tables>
GROUP BY <cols2>

GROUP BY
SELECT <cols1>
FROM <tables>
GROUP BY <cols2>
• Every entry in <cols1> must be in
<cols2>, be a constant, or be an
aggregate function
• You can have WHERE or ORDER BY
clauses as well as a GROUP BY clause

GROUP BY
Grades
Name Code Mark
John DBS 56
John IAI 72
Mary DBS 60
Mark PR1 43
Mark PR2 35
Jane IAI 54
SELECT Name,
AVG(Mark) AS Average
FROM Grades
GROUP BY Name
Name Average
John 64
Mary 60
Mark 39
Jane 54

GROUP BY
• Find the total value of the sales for
each department in each month
– Can group by Month then Department or
Department then Month
– Same results, but in a different order
Month Department Value
March Fiction 20
March Travel 30
March Technical 40
April Fiction 10
April Fiction 30
April Travel 25
April Fiction 20
May Fiction 20
May Technical 50
Sales

GROUP BY
Month Department Total
April Fiction 60
April Travel 25
March Fiction 20
March Technical 40
March Travel 30
May Fiction 20
May Technical 50
SELECT Month, Department,
SUM(Value) AS Total
FROM Sales
GROUP BY Month, Department
Month Department Total
April Fiction 60
March Fiction 20
May Fiction 20
March Technical 40
May Technical 50
April Travel 25
March Travel 30
SELECT Month, Department,
SUM(Value) AS Total
FROM Sales
GROUP BY Department, Month

HAVING
• HAVING is like a WHERE clause, except
that it applies to the results of a
GROUP BY query
• It can be used to select groups which
satisfy a given condition
SELECT Name,
FROM Grades
GROUP BY Name
HAVING AVG(Mark) >= 40
Name Average
John 64
Mary 60
Jane 54

WHERE and HAVING
• WHERE refers to the rows of tables,
and so cannot use aggregate functions
• HAVING refers to the groups of rows,
and so cannot use columns which are
not in the GROUP BY
• Think of a query being processed as
follows:
• Tables are combined
• WHERE clauses
• GROUP BY and Aggregates
• Column selection
• HAVING clauses
• ORDER BY

UNION, etc.
• UNION, INTERSECT, and EXCEPT
– These treat the tables as sets and are the
usual set operators of union, intersection,
and difference
– We’ll concentrate on UNION
– Oracle has MINUS instead of EXCEPT
• They all combine the results from two
select statements
• The results of the two selects must
have the same columns and data types

UNION
• Find, in a single query, the average
mark for each student, and the
average mark overallGrades
Name Code Mark
Jane IAI 52
John DBS 56
John IAI 72
Mark PR1 43
Mark PR2 35
Mary DBS 60

UNION
• The average for each
student:
SELECT Name,
FROM Grades
GROUP BY Name
• The average overall
SELECT
‘Total’ AS Name,
FROM Grades
• Note - this has the same
columns as the average by
student

UNION
SELECT Name
FROM Grades
GROUP BY Name
UNION
SELECT
'Total' as Name,
FROM Grades
Name Average
Jane 52
John 64
Mark 39
Mary 60
Total 53

Tables for the Example
Student
ID First Last Year
Module
Code Title Credits
Grade
ID Code Mark YearTaken

We’ll Need a UNION
• Finalists are treated differently
– Write one query for the finalists
– Write a second query for the first and
second years
– Use a UNION to join them together
<QUERY FOR FINALISTS>
UNION
<QUERY FOR OTHERS>

We’ll need to Join the Tables
• Both of the subqueries need
information from all the tables
– The student ID, name and year
– The marks for each module and the year
taken
– The number of credits for each module
• This is a natural join operation
– We could use a NATURAL JOIN statement,
and hope that our version of SQL can do it
– Safer to just use a WHERE clause

The Query So Far
SELECT <some information>
FROM Student, Module, Grade
WHERE Student.ID = Grade.ID
AND Module.Code = Grade.Code
AND <student is in third year>
UNION
SELECT <some information>
AND <student is in first or second year>

Information for Finalists
•We need to retrieve
– Compute average mark, weighted 40-60
across years 2 and 3
– First year marks need to be ignored
– The ID, Name, and Year are needed as they
are used for ordering
• The average is hard
– We don’t have any statement to separate
years 2 and 3 easily
– We can exploit the fact that 40 = 20*2 and
60 = 20*3, so YearTaken and the weighting
have a simple relationship

Information for Finalists
SELECT Year, Student.ID, Last, First,
SUM((20*YearTaken/100)*Mark*Credits)/120
AS AverageMark
AND YearTaken IN (2,3)
AND Year = 3
GROUP BY Year, Student.ID, First, Last

Information for Other Students
• Other students are easier than finalists
– We just need to average their marks where YearTaken and Year are
the same
– As before we need the ID, Name, and Year for ordering

Information for Other Students
SUM(Mark*Credits)/120 AS AverageMark
AND YearTaken = Year
AND Year IN (1,2)

The Final Query
SUM((20*YearTaken/100)*Mark*Credits)/120 AS AverageMark
WHERE Student.ID = Grade.ID AND Module.Code = Grade.Code
AND YearTaken IN (2,3) AND Year = 3
UNION
SUM(Mark*Credits)/120 AS AverageMark
WHERE Student.ID = Grade.ID AND Module.Code = Grade.Code
AND YearTaken = Year AND Year IN (1,2)
ORDER BY Year desc, AverageMark desc, First, Last, ID

Tutorial https://www.techonthenet.com/sql/select.php

SQL logical operators

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