Transact-SQL

SECTION 6

Based on SQL (1992)

Introduction

• Most important relational data manipulation language

• ANSI

• Used by many commercial databases

• 1992 ANSI standard

• SQL3

• SEQUEL

• An interactive query language

• Or embedded in other languages

• SQL is not a programming language

• Transact-SQL

• JUNIOR (Snum, Name, Major)• HONOUR-STUDENT (Number, Name, Interest)• STUDENT (SID, Name, Major, GradeLevel, Age)• CLASS (Name, Time, Room)• ENROLLMENT ( StudentNumber, ClassName, PositionNumber)• FACULTY (FID, Name, Department)

• Relations used for SQL examples

Is there a problem with the ENROLLMENT table and the primary key?

Creating a TableCREATE TABLE STUDENT(SID NUMERIC(3) CONSTRAINT student_pk PRIMARY KEY,Name nVARCHAR(20),Major nVARCHAR(3),GradeLevel nVARCHAR(2),Age NUMERIC(3))

CREATE TABLE ENROLLMENT(StudentNumber NUMERIC(3),ClassName nVARCHAR(6),CONSTRAINT enrollment_pk (StudentNumber, ClassName) PRIMARY KEY,PositionNumber NUMERIC(2),CONSTRAINT student_fk REFERENCES STUDENT (StudentNumber),CONSTRAINT class_fk REFERENCES CLASS (ClassName))

Inserting Values

INSERT INTO STUDENT VALUES(100, ‘JONES’, ‘HISTORY’, ‘GR’, 21)INSERT INTO STUDENT VALUES(150, ‘PARKS’, ‘ACCOUNTING’, ‘SO’, 19)INSERT INTO STUDENT VALUES(200, ‘BAKER’, ‘MATH’, ‘GR’, 50)INSERT INTO STUDENT VALUES(250, ‘GLASS’, ‘HISTORY’, ‘SN’, 50)INSERT INTO STUDENT VALUES(300, ‘BAKER’, ‘ACCOUNTING’, ‘SN’, 41)INSERT INTO STUDENT VALUES(350, ‘RUSSELL’, ‘MATH’, ‘JR’, 20)INSERT INTO STUDENT VALUES(400, ‘RYE’, ‘ACCOUNTING’, ‘FR’, 18)INSERT INTO STUDENT VALUES(450, ‘JONES’, ‘HISTORY’, ‘SN’, 24)

Querying a Single Table

• SQL is a transform-oriented language

• Accepts as input

• The result?

STUDENT

SID Name Major GradeLevel Age

100 JONES HISTORY GR 21

150 PARKS ACCOUNTING SO 19

200 BAKER MATH GR 50

250 GLASS HISTORY SN 50

300 BAKER ACCOUNTING SN 41

350 RUSSELL MATH JR 20

400 RYE ACCOUNTING FR 18

450 JONES HISTORY SN 24

• Sample Data

ENROLLMENT

StudentNumber ClassName PositionNumber

100 BD445 1

150 BA200 1

200 BD445 2

200 CS250 1

300 CS150 1

400 BA200 2

400 BF410 1

400 CS250 2

450 BA200 3

CLASS

Name Time Room

BA200 M-F9 SC110

BD445 MWF3 SC213

BF410 MWF8 SC213

CS150 MWF3 EA304

CS250 MWF12 EB210

Projections Using SQL

• Specified in SQL

SELECT SID, Name, Major

FROM STUDENT

SELECT STUDENT.SID, STUDENT.Name, STUDENT.Major

FROM STUDENT

SELECT s.SID, s.Name, s.Major

FROM STUDENT s

• The projection – STUDENT [SID, NAME, MAJOR]

100 JONES HISTORY

150 PARKS ACCOUNTING

200 BAKER MATH

250 GLASS HISTORY

300 BAKER ACCOUNTING

350 RUSSELL MATH

400 RYE ACCOUNTING

450 JONES HISTORY

• The result

• The word SELECT

Another Example

SELECT Major

FROM STUDENT

A HISTORY

ACCOUNTING

MATH

HISTORY

ACCOUNTING

MATH

ACCOUNTING

HISTORY

B HISTORY

ACCOUNTING

MATH

SELECT DISTINCT Major

FROM STUDENT

Selections Using SQL

• Specified in SQL

SELECT SID, Name, Major, GradeLevel, Age

FROM STUDENT

WHERE Major = ‘Math’

• The Relational Algebra selection operator is also performed

• SELECT - FROM - WHERE

SELECT *

FROM STUDENT

WHERE Major = ‘Math’

200 BAKER MATH GR 50

350 RUSSELL MATH JR 20

• Combination of Selection and Projection

SELECT Name, Age

FROM STUDENT

WHERE Major = ‘Math’

BAKER 50

RUSSELL 20

• Conditions in a WHERE clause

SELECT Name, Age

FROM STUDENT

WHERE Major = ‘Math’ AND Age > 21

BAKER 50

• Conditions in a WHERE clause can refer to a set of values

SELECT Name

FROM STUDENT

WHERE Major IN (‘Math’, ‘ACCOUNTING’)

PARKS

BAKER

BAKER

RUSSELL

RYE

• The following expression

SELECT Name

FROM STUDENT

WHERE Major NOT IN (‘Math’, ‘ACCOUNTING’)

JONES

GLASS

JONES

• WHERE clause and ranges of values

SELECT Name, Major

FROM STUDENT

WHERE Age BETWEEN 19 AND 30

JONES HISTORY

RUSSELL MATH

JONES HISTORY

• Equivalent to:SELECT Name, Major

FROM STUDENT

WHERE Age > 19 AND Age < 30

• WHERE clause and the LIKE keyword

SELECT Name, GradeLevel

FROM STUDENT

WHERE GradeLevel LIKE ‘_R’

JONES GR

BAKER GR

RUSSELL JR

RYE FR

• Finding last names ending with S

SELECT Name

FROM STUDENT

WHERE Name LIKE ‘%S’

JONES

PARKS

GLASS

JONES

• IS NULL keyword

SELECT Name

FROM STUDENT

WHERE GradeLevel IS NULL

• What will this return?

Sorting

• Rows of a result can be sorted

SELECT Name, Major, Age

FROM STUDENT

WHERE Major = ‘Accounting’

ORDER BY Name

BARKER ACCOUNTING 41

PARKS ACCOUNTING 19

RYE ACCOUNTING 18

• Sorting more than one column

SELECT Name, Major, Age

FROM STUDENT

WHERE GradeLevel IN (‘FR’, ‘SO’, ‘SN’)

ORDER BY Major ASC, Age DESC

BARKER ACCOUNTING 41

PARKS ACCOUNTING 19

RYE ACCOUNTING 18

GLASS HISTORY 50

JONES HISTORY 24

CAST & CONVERT

• Both of these functions change data values

CAST

Syntax CAST(expression as [datatype])

COURSE

SID Name Course Mark

100 JONES Actg4P87 82.4

SELECT SID, Name, Course CAST(Mark as Integer) Int_Mark FROM COURSE

COURSE

SID Name Course Int_Mark

100 JONES Actg4P87 82

CONVERT

Syntax CCONVERT(datatype, expression, [style])

COURSE

SID Name Course Mark

100 JONES Actg4P87 82.4

SELECT SID, Name, Course CONVERT(Integer, Mark) Int_Mark FROM COURSE

COURSE

SID Name Course Int_Mark

100 JONES Actg4P87 82

CAST & CONVERT with Datetime2

Datetime2 datatypeDATETIME2 can store century, year, month, date, hour, minute, and second, represented in both character and number datatypes.

DateOfBith is a Datetime2 datatype

Declare as: DateOfBirth DATETIME2

Stored as YYYY-MM-DD hh:mm:ss.n

STUDENT

SID Name DateOfBirth

100 JONES 1985-03-16 16:25:30.0000000

Datetime2 datatypes can easily be modified using CAST or CONVERT

Select SID, Name, CAST(DateOfBirth as nVARCHAR(10)) Date

FROM STUDENT.

STUDENT

SID Name Date

100 JONES 1985-03-16

Or:Select SID, Name, CONVERT(nVARCHAR(10), DateOfBirth)) Date

FROM STUDENT.

CONVERT using styles

Style Appearance Style Appearance

0 mon dd yyyy hh:miAM (or PM) 100 mon dd yyyy hh:miAM (or PM)

1 mm/dd/yy 101 mm/dd/yyyy

2 yy.mm.dd 102 yyyy.mm.dd

3 dd/mm/yy 103 dd/mm/yyyy

4 dd.mm.yy 104 dd.mm.yyyy

5 dd-mm-yy 105 dd-mm-yyyy

6 dd mon yy 106 dd mon yyyy

7 Mon dd, yy 107 Mon dd, yyyy

8 hh:mi:ss 108 hh:mi:ss

9 mon dd yyyy hh:mi:ss:mmmAM (or PM) 109 mon dd yyyy hh:mi:ss:mmmAM (or PM)

10 mm-dd-yy 110 mm-dd-yyyy

11 yy/mm/dd 111 yyyy/mm/dd

12 yymmdd 112 yyyymmdd

13 dd mon yyyy hh:mi:ss:mmm(24h) 113 dd mon yyyy hh:mi:ss:mmm(24h)

14 hh:mi:ss:mmm(24h) 114 hh:mi:ss:mmm(24h)

Select SID, Name, CONVERT(nVARCHAR(10), DateOfBirth),107) Date

FROM STUDENT.

STUDENT

SID Name DateOfBirth

100 JONES Mar 6, 1985

Select SID, Name, CONVERT(nVARCHAR(10), DateOfBirth),111) Date

FROM STUDENT.

STUDENT

SID Name DateOfBirth

100 JONES 1985/03/16

Datetime Functions

• GETDATE

– Returns the current database system date and time

– E.G. SELECT GETDATE() as ‘Current Date & Time’

• GETUTCDATE

– Returns the Coordinated Universal Time (UTC)

– E.G. SELECT GETUTCDATE() as ‘GMT Date & Time’

Current Date & Time

2015-03-23 14:43:33.470

GMT Date & Time

2015-03-23 18:43:33.470

• DATEDIFF

– Returns the time between two dates as a signed integer

– Syntax:

DATEDIFF (datepart, startdate, enddate)

datepart Abbreviation

year yy, yyyy

quarter qq, q

month mm, m

dayofyear dy, y

day dd, d

week wk, ww

weekday dw, w

hour hh

minute mi, n

second ss, s

millisecond ms

microsecond mcs

nanosecond ns

SELECT DATEDIFF (dy, ‘2015-02-15’, ‘2015-03-20’) as ‘No. of Days’

No. of Days

33

• DATEADD− Adds or subtracts a specified time interval from a date.– Syntax:

• DATEADD (datepart, number, date)

SELECT DATEADD(dy,30,GETDATE())

(NO COLUMN NAME)

2015-04-22 15:00:07.043

• DATEPART– Returns a single part of a datetime field.– Syntax:

DATEPART (datepart, date)

SELECT DATEPART (yyyy, GETDATE()) as Year,

DATEPART (mm, GETDATE()) as Month,

DATEPART (dd, GETDATE()) as Day

Year Month Day

2015 3 23

SQL Built-In Functions

• Functions

– COUNT, SUM, AVG, MAX, and MIN

SELECT COUNT (*)

FROM STUDENT

8

• Consider the following

SELECT COUNT (Major)

FROM STUDENT

vs.

SELECT COUNT (DISTINCT Major)

FROM STUDENT

8

3

Built-In Functions and Grouping

• To increase built-in function utility

• Formed by collecting rows that have the same value of a specified column

• GROUP BY

• An example

SELECT Major, COUNT (*)

FROM STUDENT

GROUP BY Major

HISTORY 3

ACCOUNTING 3

MATH 2

• Grouping subsets

SELECT Major, COUNT (*)

FROM STUDENT

GROUP BY Major

HAVING COUNT (*) > 2

HISTORY 3

ACCOUNTING 3

• Greater generality using WHERE

SELECT Major, AVG (Age)

FROM STUDENT

WHERE GradeLevel = ‘SN’

GROUP BY Major

HAVING COUNT (*) > 1

HISTORY 37

Try the following:

SELECT SUM(Cost) as SumCostFROM ORDERS

SELECT SUM(Cost) as SumCost, OrderNumFROM ORDERS

This does not work

SELECT SUM(Cost) OVER () AS SumCost, OrderNumFROM Orders

OVER and PARTITIONING

ORDERS

OrderNum CustomerNo Cost

345 1 7.50

346 1 8.50

347 1 9.50

348 2 8.00

SumCost

33.50

SumCost OrderNum

33.50 345

33.50 346

33.50 347

33.50 348

OVER allows you to get aggregate information without using a GROUP BY. In other words, you can retrieve detail rows, and get aggregate data alongside it.

Quick translation:SUM(cost) – get me the sum of the COST columnOVER – for the set of rows….() – …that encompasses the entire result set.

OVER exposes the entire resultset to the aggregation…”SumCost” was the sum of all [Cost]  in the resultset.  We can break up that resultset into partitions with the use of PARTITION BY:

SELECT SUM(Cost) OVER (PARTITION BY CustomerNo) AS SumCost, OrderNum, CustomerNoFROM Orders

The partition is by CustomerNo – each “window” of a single customer’s orders will be treated separately from each other “window”.This will give the sum of cost for Customer 1, and then the sum for Customer 2.

The translation here is:SUM(cost) – get me the sum of the COST columnOVER – for the set of rows….(PARTITION BY CustomerNo) – …that have the same CustomerNo.

SumCost OrderNum CustomerNo

25.50 345 1

25.50 346 1

25.50 347 1

8.00 348 2

Querying Multiple Tables

• Study now extended to two or more tables

• Will use the data from the following tables

• STUDENT (SID, Name, Major, GradeLevel, Age)• CLASS (Name, Time, Room)• ENROLLMENT ( StudentNumber, ClassName, PositionNumber)

Retrieval Using Subquery

SELECT StudentNumber

FROM ENROLLMENT

WHERE ClassName = ‘BD445’

100

200

SELECT Name

FROM STUDENT

WHERE SID IN (100,200)

• Want to know the names of the students enrolled in class BD445

• Use it as a subquery

JONES

BAKER

SELECT Name

FROM STUDENT

WHERE SID IN

(SELECT StudentNumber

FROM ENROLLMENT

WHERE ClassName = ‘BD445’)

• Subqueries can consist of three or more tables

100

200

300

SELECT ENROLLMENT.StudentNumber

FROM ENROLLMENT

WHERE ENROLLMENT.ClassName IN

(SELECT CLASS.Name

FROM CLASS

WHERE ClassTime = ‘MWF3’)

• To get the names of the students

JONES

BAKER

BAKER

SELECT STUDENT.Name

FROM STUDENT

WHERE STUDENT.SID IN

(SELECT ENROLLMENT.StudentNumber

FROM ENROLLMENT

WHERE ENROLLMENT.ClassName IN (SELECT CLASS.Name

FROM CLASS

WHERE ClassTime = ‘MWF3’))

Joining With SQL – The Inner Join

• A join that displays only the rows that have a match in both the joined tables

• Want to produce SID, StudentName, and ClassName for every student

• What two tables must be joined?

• Looking for equality between STUDENT.SID and ENROLLMENT. StudentNumber

SELECT STUDENT.SID, STUDENT.Name, ENROLLMENT.ClassName

FROM STUDENT, ENROLLMENT

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

SELECT s.SID, s.Name, e.ClassName

FROM STUDENT s -- left join table

INNER JOIN ENROLLMENT e --right join table

ON s.SID = e.StudentNumber

SELECT s.SID, s.Name, e.ClassName

FROM STUDENT s -- left join table

JOIN ENROLLMENT e --right join table

ON s.SID = e.StudentNumber

http://www.codeproject.com/Tips/712941/Types-of-Join-in-SQL-Server

• Alternative Syntax

• What operations make up a join?

• FROM equates to

• WHERE expresses

100 JONES BD445

150 PARKS BA200

200 BAKER BD445

200 BAKER CS250

300 BAKER CS125

400 RYE BA200

400 RYE BF410

400 RYE CS250

450 JONES BA200

• The WHERE clause and qualifiers

400 RYE BF410

SELECT STUDENT.SID, ENROLLMENT.ClassName

FROM STUDENT, ENROLLMENT

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

AND STUDENT.Name = ‘RYE’

AND ENROLLMENT.PositionNumber = 1

• Data from more than two tables

200 BD445 MWF3 2

200 CS250 MWF12 1

300 CS150 MWF3 1

SELECT STUDENT.SID, CLASS.Name, CLASS.Time

ENROLLMENT.ClassName

FROM STUDENT, ENROLLMENT, CLASS

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

AND ENROLLMENT.ClassName = CLASS.Name

AND STUDENT.Name = ‘BAKER’

Need to create two new tables:

EMPLOYEE:

CREATE TABLE EMPLOYEE(EmployeeNumber INTEGER IDENTITY(100,1) CONSTRAINT emp_pk PRIMARY KEY,FirstName nVARCHAR(20),LastName nVARCHAR(20),DepartID INTEGER,ManagerId INTEGER)

DEPARTMENT:

CREATE TABLE DEPARTMENT(DeptId INTEGER IDENTITY(1,1) CONSTRAINT dept_pk PRIMARY KEY,DepartmentName nVARCHAR(10))

Other type of Joins

What is IDENTITY?

Syntax IDENTITY (seed, increment)

A function that generates an Identity Column.

An Identity Column is a column in a table that is made up of values generated by the database. This is much like an autonumber Field in Microsoft Access or a sequence in Oracle. It is an important concept in database, implemented by many RDBMS, although each has its own terminology.

Identity is an auto-increment function that allows a unique number to be generated when a new record is inserted into a table.

DeptId DepartmentName

1 Accounting

2 Marketing

3 Finance

4 Sales

5 IT

INSERT INTO DEPARTMENT VALUES('Accounting')INSERT INTO DEPARTMENT VALUES('Marketing')INSERT INTO DEPARTMENT VALUES('Finance')INSERT INTO DEPARTMENT VALUES('Sales')INSERT INTO DEPARTMENT VALUES('IT')

INSERT INTO EMPLOYEE VALUES('Sheldon', 'White',1,NULL)INSERT INTO EMPLOYEE VALUES('Geraldine', 'Summers',1,107)INSERT INTO EMPLOYEE VALUES('Gillian', 'Hall',1,107)INSERT INTO EMPLOYEE VALUES('William', 'Hancock',2,100)INSERT INTO EMPLOYEE VALUES('Sheila', 'Tunning',3,105)INSERT INTO EMPLOYEE VALUES('Waylon', 'Hart',3,100)INSERT INTO EMPLOYEE VALUES('Jennifer', 'Albacore',3,105)INSERT INTO EMPLOYEE VALUES('Harold', 'Spring',1,100)INSERT INTO EMPLOYEE VALUES('Lenny', 'Carling',NULL,100)

EmployeeNumber FirstName LastName DepartId ManagerId

100 Sheldon White 1 NULL

101 Geraldine Summers 1 107

102 Gillian Hall 1 107

103 William Hancock 2 100

104 Sheila Tunning 3 105

105 Waylon Hart 3 100

106 Jennifer Albacore 3 105

107 Harold Spring 1 100

108 Lenny Carling NULL 100

Left Outer Join

Displays all the rows from first table and matched rows from second tableSyntax:

SELECT * FROM Employee eLEFT OUTER JOIN Department dON e.DepartID = d.DeptId

EmployeeNumber FirstName LastName DepartId ManagerId DeptId DepartmentName

100 Sheldon White 1 NULL 1 Accounting

101 Geraldine Summers 1 107 1 Accounting

102 Gillian Hall 1 107 1 Accounting

103 William Hancock 2 100 2 Marketing

104 Sheila Tunning 3 105 3 Finance

105 Waylon Hart 3 100 3 Finance

106 Jennifer Albacore 3 105 3 Finance

107 Harold Spring 1 100 1 Accounting

108 Lenny Carling NULL 100 NULL NULL

Right Outer Join

Displays all the rows of second table and matched rows from first table

SELECT * FROM EMPLOYEE eRIGHT OUTER JOIN Department dON e.DepartID = d.DeptId

EmployeeNumber FirstName LastName DepartId ManagerId DeptId DepartmentName

100 Sheldon White 1 NULL 1 Accounting

101 Geraldine Summers 1 107 1 Accounting

102 Gillian Hall 1 107 1 Accounting

107 Harold Spring 1 100 1 Accounting

103 William Hancock 2 100 2 Marketing

104 Sheila Tunning 3 105 3 Finance

105 Waylon Hart 3 100 3 Finance

106 Jennifer Albacore 3 105 3 Finance

NULL NULL NULL NULL NULL 4 Sales

NULL NULL NULL NULL NULL 5 IT

Full Outer Join

Full outer join returns all the rows from both tables whether it has been matched or not

SELECT * FROM Employee eFULL OUTER JOIN Department dON e.DepartID = d.DeptId

EmployeeNumber FirstName LastName DepartId ManagerId DeptId DepartmentName

100 Sheldon White 1 NULL 1 Accounting

101 Geraldine Summers 1 107 1 Accounting

102 Gillian Hall 1 107 1 Accounting

103 William Hancock 2 100 2 Marketing

104 Sheila Tunning 3 105 3 Finance

105 Waylon Hart 3 100 3 Finance

106 Jennifer Albacore 3 105 3 Finance

107 Harold Spring 1 100 1 Accounting

108 Lenny Carling NULL 100 NULL NULL

NULL NULL NULL NULL NULL 4 Sales

NULL NULL NULL NULL NULL 5 IT

Cross Join

Cartesian product The size of a Cartesian product is the number of the rows in the first table multiplied by the number of rows in the second table

SELECT * FROM EMPLOYEECROSS JOIN DEPARTMENT

This table will have 45rows and seven columns

Self Join Joining the table itself called self join or theta join. A self join is used to retrieve the records having some relation or similarity with other records in the same table. Need to use aliases for the same table to set a self join between single table and retrieve records satisfying the condition in where clause.

SELECT e1.EmployeeNumber,e1.FirstName, e1.LastName,e2.EmployeeNumber as ManagerId, e2.FirstName, e2.LastNameFROM EMPLOYEE e1INNER JOIN EMPLOYEE e2ON e1.ManagerId = e2.EmployeeNumber

EmployeeNumber FirstName LastName ManagerId FirstName LastName

101 Geraldine Summers 107 Harold Spring

102 Gillian Hall 107 Harold Spring

103 William Hancock 100 Sheldon White

104 Sheila Tunning 105 Waylon Hart

105 Waylon Hart 100 Sheldon White

106 Jennifer Albacore 105 Waylon Hart

107 Harold Spring 100 Sheldon White

108 Lenny Carling 100 Sheldon White

SELECT CONCAT(e1.EmployeeNumber,' - ',e1.FirstName,' ', e1.LastName) as Employee,CONCAT(e2.EmployeeNumber,' - ', e2.FirstName,' ', e2.LastName) as ManagerFROM EMPLOYEE e1INNER JOIN EMPLOYEE e2ON e1.ManagerId = e2.EmployeeNumber

Employee Manager

101 – Geraldine Summers 107 – Harold Spring

102 – Gillian Hall 107 – Harold Spring

103 – William Hancock 100 – Sheldon White

104 – Sheila Tunning 105 – Waylon Hart

105 – Waylon Hart 100 – Sheldon White

106 – Jennifer Albacore 105 – Waylon Hart

107 – Harold Spring 100 – Sheldon White

108 – Lenny Carling 100 – Sheldon White

Comparison of SQL Subquery and Join

• A join is an alternative to expressing many subqueries

• For example, “Classes taken by undergrads?”

SELECT DISTINCT ENROLLMENT.ClassName

FROM ENROLLMENT, STUDENT

WHERE ENROLLMENT.StudentNumber = STUDENT.SID

AND STUDENT.Grade.Level NOT = ‘GR’

• As a subquery

SELECT DISTINCT Class.Name

FROM ENROLLMENT

WHERE StudentNumber IN

(SELECT SID

FROM STUDENT

WHERE GradeLevel NOT = ‘GR’)

• If we want to know:“Class names and grade levels of undergrads?”

SELECT DISTINCT ENROLLMENT.ClassName, SUDENT.GradeLevel

FROM ENROLLMENT, STUDENT

WHERE ENROLLMENT.StudentNumber = STUDENT.SID

AND STUDENT.GradeLevel NOT = ‘GR’

BA200 SO

CS150 SN

BA200 FR

BF410 FR

CS250 FR

BA200 SN

•Why cannot a subquery be used?

• Thus in the previous subquery example:SELECT DISTINCT Class.Name

FROM ENROLLMENT

WHERE StudentNumber IN

(SELECT SID

FROM STUDENT

WHERE GradeLevel NOT = ‘GR’)

• This would not work:

SELECT DISTINCT ENROLLMENT.ClassName, STUDENT.GradeLevel

FROM ENROLLMENT

WHERE StudentNumber IN

(SELECT SID

FROM STUDENT

WHERE GradeLevel NOT = ‘GR’)

Creating a ViewA view is a virtual table based on the result of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

A view can consist of table columns, aggregates, constants, and computed columns.

SYNTAX: CREATE VIEW view_nameASSELECT column_name(s)FROM table_nameWHERE condition

SELECT STUDENT.SID, STUDENT.Name, ENROLLMENT.ClassName

FROM STUDENT, ENROLLMENT

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

CREATE VIEW StudentClass

AS

SELECT STUDENT.SID, STUDENT.Name, ENROLLMENT.ClassName

FROM STUDENT, ENROLLMENT

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

100 JONES BD445

150 PARKS BA200

200 BAKER BD445

200 BAKER CS250

300 BAKER CS125

400 RYE BA200

400 RYE BF410

400 RYE CS250

450 JONES BA200

CREATE VIEW StudentClass

AS

SELECT STUDENT.SID, STUDENT.Name, ENROLLMENT.ClassName

FROM Server1.CompantData.dbo.STUDENT, Server2.CompantData.dbo.ENROLLMENT

WHERE STUDENT.SID = ENROLLMENT.StudentNumber

Name MinSalary MaxSalary AvgSalary EmpsPerDept ----------------------------- --------------------- --------------------- --------------------- ---------------- Executive 39.06 125.50 68.3034 4 Finance 13.4615 43.2692 23.935 10 Human Resources 13.9423 27.1394 18.0248 6 Information Services 27.4038 50.4808 34.1586 10 Marketing 13.4615 37.50 18.4318 11 Production 6.50 84.1346 13.5537 195 Purchasing 9.86 30.00 18.0202 14 Research and Development 40.8654 50.4808 43.6731 4 Sales 23.0769 72.1154 29.9719 18 Shipping and Receiving 9.00 19.2308 10.8718 6

SELECT DISTINCT Name,MIN(Rate) OVER (PARTITION BY edh.DepartmentID) AS MinSalary,MAX(Rate) OVER (PARTITION BY edh.DepartmentID) AS MaxSalary,AVG(Rate) OVER (PARTITION BY edh.DepartmentID) AS AvgSalary,COUNT(edh.BusinessEntityID) OVER (PARTITION BY edh.DepartmentID) AS

EmpsPerDeptFROM HR.EmployeePayHistory eph, HR.EmployeeDepartmentHistory edh, HR.Department dWHERE eph.BusinessEntityID = edh.BusinessEntityIDAND d.DepartmentID = edh.DepartmentIDAND edh.EndDate IS NULLORDER BY Name

Advantages of views:

1.Database Views can represent a subset of the data contained in a table and thus can limit the degree of exposure of the underlying tables to the outside world. A user may have permission to query the view, while denied access to the rest of the base table.

2.Views can join and simplify multiple tables into a single virtual table.

3.Views can act as aggregated tables, where the database engine aggregates data ( sum , average, etc.) and presents the calculated results as part of the data.

4.Views can hide the complexity of data. For example, a view could appear as Sales2000 or Sales2001, transparently partitioning the actual underlying table.

5.Views take very little space to store; the database contains only the definition of a view, not a copy of all the data that it presents.

6.Depending on the SQL engine used, views can provide extra security.

EXISTS and NOT EXISTS

• Logical operators

SELECT DISTINCT StudentNumber

FROM ENROLLMENT A

WHERE EXISTS

(SELECT *

FROM ENROLLMENT B

WHERE A.StudentNumber = B.StudentNumber

AND A.ClassName NOT = B.ClassName)

• Both query and subquery refer to the same table

• Two uses assigned a different name

• What is the meaning of the subquery?

• General procedure:

• First row in A is compared with first row in B

• First Row in A compared with second row in B

200

400

• NOT EXISTS operator

SELECT STUDENT.Name

FROM STUENT

WHERE NOT EXISTS

(SELECT *

FROM ENROLLMENT

WHERE NOT EXISTS

(SELECT *

FROM CLASS

WHERE CLASS.Name = ENROLLMENT.ClassName

AND ENROLLMENT.StudentNumber = STUDENT.SID))

• Query has three parts

CONCAT

Enables the concatenation, or linking together, of two or more string values into a single string. The output is VCHAR or nVARCHAR.

Syntax: CONCAT(string_value1, string_value2, ……string_valueN)

STUDENT

SID Name Major GradeLevel Age

100 JONES HISTORY GR 21

150 PARKS ACCOUNTING SO 19

200 BAKER MATH GR 50

250 GLASS HISTORY SN 50

300 BAKER ACCOUNTING SN 41

350 RUSSELL MATH JR 20

400 RYE ACCOUNTING FR 18

450 JONES HISTORY SN 24

SELECT CONCAT(SID, ‘-’, Name) as ‘Number & Name’, Major

FROM STUDENT

Number & Name Major

100-JONES HISTORY

150-PARKS ACCOUNTING

200-BAKER MATH

250-GLASS HISTORY

300-BAKER ACCOUNTING

350-RUSSELL MATH

400-RYE ACCOUNTING

450-JONES HISTORY

Changing Data

Inserting Data

• Inserting a single row

INSERT INTO ENROLLMENT

VALUES (400, ‘BD445’, 44)

• Some data in a row not known

INSERT INTO ENROLLMENT

(StudentNumber, ClassName)

VALUES (400, ‘BD445’)

• Mass copy rows

INSERT INTO JUNIOR (SID, Name, Major)

SELECT SID, Name, Major

FROM STUDENT

WHERE GradeLevel = ‘JR’

Deleting Data

• Can be deleted one at a time

DELETE STUDENT

WHERE STUDENT.SID = 100

• Groups of rows can be deleted

DELETE ENROLLMENT

WHERE ENROLLMENT.StudentNumber IN

(SELECT STUDENT.SID

FROM STUDENT

WHERE STUDENT.Major = ‘Accounting’)

DELETE STUDENT

WHERE STUDENT.Major = ‘Accounting’

Modifying Data

• Rows can be modified one at a time

UPDATE ENROLLMENT

SET PositionNumber = 44

WHERESID = 400

UPDATE ENROLLMENT

SET PositionNumber = MAX (PositionNumber) + 1

WHERESID = 400

• Mass Updates

UPDATE ENROLLMENT

SET ClassName = ‘BD564’

WHERE ClassName = ‘BD445’

UPDATE CLASS

SET ClassName = ‘BD564’

WHERE ClassName = ‘BD445’

Summary

• Importance of SQL

• Operations on a single table

• Operations on two or more tables