module 10 summarizing data

8/9/2019 Module 10 Summarizing Data

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Module 10:Summarizing Data

Vidya Vrat Agarwal. | MCT, MCSD


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Overview

Using Aggregate Functions

GROUP BY Fundamentals

Generating Aggregate Values Within Result Sets

Using the COMPUTE and COMPUTE BY Clauses

Listing the TOP n Values


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Aggregate function

Aggregate functionAggregate function Description

DescriptionDescription

AVG

AVG Average of values in a numeric expression

Average of values in a numeric expression

COUNT

COUNT Number of values in an expression

Number of values in an expression

COUNT (*)

COUNT (*) Number of selected rows

Number of selected rows

MAX

MAX Highest value in the expression

Highest value in the expression

MIN

MIN Lowest value in the expression

Lowest value in the expression

SUM

SUM Total values in a numeric expression

Total values in a numeric expression


A functions that performs a calculation on a column in a

set of rows and returns a single value.


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Using Aggregate Functions with Null Values

Most Aggregate Functions Ignore Null Values

COUNT(*) Function Counts Rows with Null Values

USE northwind

SELECT COUNT (*)

FROM employees

Aggregate Query

A query (SQL statement) that summarizes informationfrom multiple rows by including an aggregate function

such as Sum or Avg .


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Using the GROUP BY Clause

Using the GROUP BY Clause with the HAVING Clause

Divides a table into groups.


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Using the GROUP BY Clause

USE northwind

SELECT productid, orderid, quantity

FROM [order details]

USE northwind

SELECT productid, SUM(quantity)

AS total_quantity


GROUP BY productid

productid

productidproductid total_quantity

total_quantitytotal_quantity

1

1 15

15

2

2 35

35

3

3 45

45

productid

productidproductid orderid

orderidorderid quantity

quantityquantity

1

1 1

1 5

5

1

1 1

1 10

10

2

2 1

1 10

10

2

2 2

2 25

25

3

3 1

1 15

15

3

3 2

2 30

30

productid

productidproductid total_quantity

total_quantitytotal_quantity

2

2 35

35Only rows thatsatisfy the WHERE

clause are groupedUSE northwind


AS total_quantity


WHERE productid = 2

GROUP BY productid

WHERE productid = 2


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Using the GROUP BY Clause with the HAVING Clause

USE northwind


AS total_quantity


GROUP BY productid

HAVING SUM(quantity) >=30

productidproductidproductid total_quantitytotal_quantitytotal_quantity

22 3535

33 4545

productidproductidproductid orderidorderidorderid quantityquantityquantity

11 11 55

11 11 1010

22 11 1010

22 22 2525

33 11 1515

33 22 3030

Server: Msg 147, Level 15, State 1, Line 5

An aggregate may not appear in the WHERE clause


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Using the GROUP BY Clause with the ROLLUP Operator

Using the GROUP BY Clause with the CUBE Operator


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USE northwind

SELECT productid, orderid, SUM(quantity) AS total_quantity


GROUP BY productid, orderid

WITH ROLLUP

ORDER BY productid, orderid

USE northwind




WITH ROLLUP


productidproductidproductid orderidorderidorderid total_quantitytotal_quantitytotal_quantity

NULLNULL NULLNULL 9595

11 NULLNULL 1515

11 11 55

11 22 1010

22 NULLNULL 353522 11 1010

22 22 2525

33 NULLNULL 4545

33 11 1515

33 22 3030


Grand totalGrand total

Summarizes only rows for productid 1Summarizes only rows for productid 1

Detail value forproductid 1, orderid 1Detail value forproductid 1, orderid 1








Using the GROUP BY Clause with the ROLLUP Operator


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Using the GROUP BY Clause with the CUBE Operator

USE northwind




WITH CUBE


USE northwindSELECT productid, orderid, SUM(quantity) AS total_quantity



WITH CUBE


productidproductidproductid

orderidorderidorderid

total_quantitytotal_quantitytotal_quantity

NULLNULL NULLNULL 9595

NULLNULL 11 3030

NULLNULL 22 6565

11 NULLNULL 1515

11 11 55

11 22 1010

22 NULLNULL 3535

22 11 101022 22 2525

33 NULLNULL 4545

33 11 1515

33 22 3030


Grand totalGrand total

Summarizes all rows for orderid 1Summarizes all rows for orderid 1

Summarizes all rows for orderid 2Summarizes all rows for orderid 2





Detail value forproductid 2, orderid 1Detail value forproductid 2, orderid 1Detail value forproductid 2, orderid 2Detail value forproductid 2, orderid 2




The CUBE operator

produces two

more summary

values than the

ROLLUP operator

The CUBE operator

produces two

more summary

values than the

ROLLUP operator


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USE northwind




COMPUTE SUM(quantity) BY productid

COMPUTE SUM(quantity)

USE northwind




COMPUTE SUM(quantity) BY productid


USE northwind





USE northwind





COMPUTECOMPUTE COMPUTE BYCOMPUTE BY


11 11 55

11 22 1010

22 11 1010

22 22 2525

33 11 151533 22 3030

sum 95sum 95


11 11 55

11 22 1010

sum 15sum 15

22 11 1010

22 22 2525sum 35sum 35

33 11 1515

33 22 3030

sum 45sum 45

sum 95sum 95


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Lists Only the First n Rows of a Result Set

Specifies the Range of Values in the ORDER BY Clause

Returns Ties if WITH TIES Is Used

USE northwind

SELECT TOP 5 orderid, productid, quantity


ORDER BY quantity DESC

USE northwind

SELECT TOP 5 orderid, productid, quantity



USE northwind

SELECT TOP 5 WITH TIES orderid, productid, quantity



USE northwind

SELECT TOP 5 WITH TIES orderid, productid, quantity




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Recommended Practices

Use the ORDER BY Clause to Guarantee a Sort OrderUse the ORDER BY Clause to Guarantee a Sort Order

Avoid Using the COMPUTE or COMPUTE BY ClauseAvoid Using the COMPUTE or COMPUTE BY Clause

Avoid Using Aggregate Functions with Null ValuesAvoid Using Aggregate Functions with Null Values

Use the ROLLUP Operator Whenever PossibleUse the ROLLUP Operator Whenever Possible

Index Frequently Aggregated ColumnsIndex Frequently Aggregated Columns


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Check Your Understanding.


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Q.1 What is an Aggregate Function.? Give names of thefunctions.


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Q.2. What is an Aggregate Query. ?


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Q.3. What is Group By.?


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Q.4. What is the difference between Group By and GroupBy with Having.?


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Q.5. All Aggregate Functions Ignore Null Values.

1. True

2. False


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Q.6. COUNT(*) Function Counts Rows withNull Values.

1. True2. False


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Q.7. CUBE operator produces more rows of summaryvalues than ROLLUP operator.

1. True

2. False


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Q.8. What is the difference between COMPUTE andCOMPUTE BY.?


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Q.9 Consider the following table named Salary.

500Null3500Samuel

100020004000AbrahamNullNull200Ravi

Null10002500Joseph

Null20005000Mathews

50015004500AlexisDEDUCTIONSHRABASICNAME

What will be the result of

Select COUNT(*) From Salary

a. 5 b. 6 c. 4 d. 3


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Q.10. Consider the following table named Salary.

500Null3500Samuel

100020004000Abraham

NullNull200Ravi

Null10002500Joseph

Null20005000Mathews

50015004500Alexis

DEDUCTIONSHRABASICNAME


Select COUNT(Basic) From Salary

a. 5 b. 6 c. 4 d. 3


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Q.11. Consider the following table named Salary.

500Null3500Samuel

100020004000Abraham

NullNull200Ravi

Null10002500Joseph

Null20005000Mathews

50015004500Alexis

DEDUCTIONSHRABASICNAME


Select AVG(Hra) From Salary

a. 1083.33 b.1625.00

c. 1803.33 d. None of the above


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Q.12 What will COUNT(*) return if there are no rows in thetable matching the search criteria.

a. -1

b. Null

c. 0

d. None of the above


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Q.13 SQL provides Six Aggregate Functions.

1. True

2. False


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Q.14 Keyword Distinct can be used with Count(*).

1. Yes

2. No


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Q.15. Consider the following table named Salary

500Null3500Samuel

100020004000Abraham

NullNull200Ravi

Null10002500Joseph

Null20005000Mathews

50015004500AlexisDEDUCTIONSHRABASICNAME


Select MIN(Deductions) From Salary

a. 1000 b.333.33 c. 500 d.None


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Q.16. Consider the following table named Salary

500NullD1Samuel

10002000D3Abraham

NullNullD2Ravi

Null1000D3Joseph

Null2000D1Mathews

5001500D1AlexisDEDUCTIONSHRADEPTNAME


Select AVG(HRA) From Salary where DEPT = D1

a. 1166.67 b.1750 c. 3500 d.None


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Review







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Nothing great is everachieved without enthusiasm

Thank You.

module 10 summarizing data

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