Module 07_Querying Table

8/9/2019 Module 07_Querying Table

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Module 7Querying Tables

Vidya Vrat Agarwal. | MCT, MCSD


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Overview

How Queries are Processed

Select Statement

Manipulating Column Names

Literals

Range Operator

List Operator

String Operator Wildcard

Unknown Value

ISNULL


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Submits Compiled requests for Processing and thenRun.

Execute

Translates the Query into an Executable PlanCompile

Determines the indexes to useOptimizeValidates that the names of the Objects are PresentResolve

Checks Syntax for Accuracy.Parse

DescriptionProcess


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Select Statement

Select statement is to access and retrieve data fromdatabase.

The Keywords Select, From, Where makes up the basicSelect Statement.

The basic from of the select statement sometimes called a

Mapping or a Select-from-where block.


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Selecting Data

Select name from Students

Select All name from Students

Select Distinct name from students


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When query results are displayed, a column name of theresult set is always displayed as it was specified at thetime of Table creation.

Create Table Students

( Sid int identity,

Name varchar(20)

)

Select * from Students


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A User defined Column heading can replace the defaultcolumn heading.

Select Column_alias = column_name, [Column_alias=column_name]

From table_name

Or

Select Column_name Column_alias, [Column_name Column_alias]

From table_name

Where Column_alias is the User defined column heading that is to bespecified in place of the default Column heading.


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Use Pubs

select Publishers Identity =pub_id, Publishers Name pub_name

from publishers

Publishers Identity Publishers Name

------------------- ----------------------------------------

0736 New Moon Books

0877 Binnet & Hardley

1389 Algodata Infosystems

1622 Five Lakes Publishing

1756 Ramona Publishers

9901 GGG&G

9952 Scootney Books9999 Lucerne Publishing

(8 row(s) affected)


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Literals

The result set of the data query statement can be mademore readable by including a String called Literal inSelect list enclosed in single quotes .

A Literal should typically be used before the column name

for which a string is to be displayed.

Select Column_name ,String_literal, [Column_name ,String_literal]

From table_name


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Literals

Use pubsselect pub_id,'Publishers Name is :',pub_name from publishers

pub_id pub_name

------ -------------------- ----------------------------------------

0736 Publishers Name is : New Moon Books

0877 Publishers Name is : Binnet & Hardley1389 Publishers Name is : Algodata Infosystems

1622 Publishers Name is : Five Lakes Publishing

1756 Publishers Name is : Ramona Publishers

9901 Publishers Name is : GGG&G

9952 Publishers Name is : Scootney Books

9999 Publishers Name is : Lucerne Publishing

(8 row(s) affected)


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Range Operator

The Range Operator is used to retrieve data that can beextracted in ranges.

The Range Operators are :

Between and

Not Between


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Range Operators

Use pubs

select advance,title from titles

where advance between 2000 and 4000

advance title--------------------- ------------------------------------------

2275.0000 Is Anger the Enemy?

2000.0000 Prolonged Data Deprivation: Four Case Studies

4000.0000 Emotional Security: A New Algorithm

4000.0000 Fifty Years in Buckingham Palace Kitchens

(4 row(s) affected)


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List Operator

SQL Server allows the IN operator that allows theSelection of values, that match any value in List.

The List operators are :

IN and

NOT IN

Select Column_list

From table_name

Where Column_name IN ( Value_list)


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List Operators

Use pubs

select pub_name, city,state

from publishers

where state IN ('MA','DC')

pub_name city state

---------------------------------------- -------------------- -----

New Moon Books Boston MA

Binnet & Hardley Washington DC

(2 row(s) affected)


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String Operator - Wildcard

SQL Server provides a Pattern-Matching method for stringexpressions using LIKE Keyword with the Wildcard mechanism.

single character not within specified range. [^a - f][^]

single character within specified range. [a-f] or [abcdef][ ]

Represents a Single Character._(UnderScore)

Represents any string of zero or more character (s)%

DescriptionWildcard


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Enclose the wildcard(s) and the character string in single quotation marks, for example:

LIKE 'Mc%' searches for all strings that begin with the letters Mc (McBadden).

LIKE '%inger' searches for all strings that end with the letters inger (Ringer, Stringer).

LIKE '%en%' searches for all strings that contain the letters en anywhere in the string(Bennet, Green, McBadden).

LIKE '_heryl' searches for all six-letter names ending with the letters heryl (Cheryl, Sheryl).

LIKE '[CK]ars[eo]n' searches for Carsen, Karsen, Carson, and Karson (Carson).

LIKE '[M-Z]inger' searches for all names ending with the letters inger that begin with anysingle letter from M through Z (Ringer).

LIKE 'M[^c]%' searches for all names beginning with the letter M that do not have the letterc as the second letter (MacFeather).


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SELECT phone

FROM authors

WHERE phone LIKE '415%

phone

------------

415 986-7020

415 548-7723

415 834-2919

415 658-9932

415 836-7128

415 585-4620

415 935-4228

415 843-2991

415 354-7128

415 534-9219

415 836-7128

(11 row(s) affected)


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%

SELECT phone

FROM pubs.dbo.authors

WHERE phone NOT LIKE '415%'

Or

SELECT phone

FROM pubs.dbo.authorsWHERE NOT phone LIKE '415%'


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_ ( Underscore)

SELECT au_lname, au_fname, phone

FROM authors

WHERE au_fname LIKE _heryl'

au_lname au_fname phone

---------------------------------------- -------------------- ------------

Carson Cheryl 415 548-7723

Hunter Sheryl 415 836-7128

(2 row(s) affected)


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[ ]


FROM authors

WHERE au_fname LIKE '[CS]heryl'


---------------------------------------- -------------------- ------------


Hunter Sheryl 415 836-7128

(2 row(s) affected)


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[ ]


FROM authors

WHERE au_lname LIKE '[CK]ars[eo]n'


---------------------------------------- -------------------- ------------


Karsen Livia 415 534-9219

(2 row(s) affected)


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UnKnown value

Unknown values refer to the data entered in the form ofNULL keyword.

The NULL values can be retrieved from the table usingIS NULL or IS NOT NULL keyword in the where clause.

select title,ytd_salesfrom titles

where ytd_sales IS NULL

title ytd_sales

-------------------------------------------------------------------------------- -----------

The Psychology of Computer Cooking NULLNet Etiquette NULL

(2 row(s) affected)


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ISNULL

Replaces NULL with the specified replacement value.

Select title,'ytd_sales = ISNULL(ytd_sales,'0')

from titles

where ytd_sales IS NULL

title ytd_sales

---------------------------------------------------------- -----------

The Psychology of Computer Cooking 0

Net Etiquette 0

(2 row(s) affected)


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Check Your Understanding.


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Q.1. How Query is Processed.?


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Q.2. What is the Purpose of SELECT Statement.?


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Q.3. What is the difference between ALL and DISTINCT.?


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Q.4. What is Column Alias.? What is the Advantage.?


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Q.5. What is Literal and what is its purpose.?


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Q.6. What are Range Operators and what is the Purpose.?


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Q.7. What is List Operator and what is the Purpose.?


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Q.8. What are String Operators- wildcard, and what are the

types and Purpose.?


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Q.9. What is UNKNOWN value.? How this Value can be

Retrieved.?


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Q.10. What is the Purpose of ISNULL.?


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Review


Select Statement


Literals

Range Operator

List Operator

String Operator Wildcard

Unknown Value

ISNULL


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Practice is the MotherOf SkillThank You.

Documents

Module 07_Querying Table