Session6_SP_UDF

8/7/2019 Session6_SP_UDF

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Stored Procedures &

User-Defined Functions

Vu Tuyet [email protected]

Hanoi University of Technology

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Introduction to SQL Batch Processing

Batch

Individual SQL

commands

Grouped to form abatch

Compiledas singleexecutionplan


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Example

Use Pubs

Select * from authorsUpdate authors

set phone= '890 451-7366

where au_lname= 'White'

Go


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Outline

Understanding the concepts of batch and batchprocessing

T-SQL Programming Define and assign variables

Cursors for data retrieval

Control statements

Write SQL statements using SQL Server basic functions

Use basic functions in a query

Implementing Stored Procedures

Implementing User-Defined Functions

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Assigning values to variables

SET statement

SET @local_variable name = value

SELECT statementSELECT @local_variable name = value

Ex

ampleSET @CUST=FRANK

SELECT CUSTOMERID,COMPANYNAME

FROM CUSTOMERS

WHERE CUSTOMERID = @CUST


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Variables

SQL Server supports two types of variables in T-SQL

@@global_variable

@local_variable


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List of Global variables

@@CONNECTIONS Number of connections made to the server

since it was last started.

@@CPU_BUSY Number of milliseconds the system has been

processing since SQL Server was started

@@CURSOR_ROWS Number of rows in the most recently opened

cursor.

@@ERROR Error number of the last T-SQL error

@@FETCH_STATUS 0 if the last fetch status was successful.

-1 if there was an error


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Cursors to Retrieve Data

Allowing positioning at specific rows of the result set

Retrieving one row or block of rows from the current

position in the result set

Supporting data modifications to the rows at the current

position in the result set

Supporting different levels of visibility for changes made

by other users to the data in the result set

Providing access to the data in a result set for T-SQL

statements in scripts, stored procedures, and triggers


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CursorImplementations

Transact-SQL Server Cursors

Used in scripts, stored procedures, and triggers

Implemented on the server

API Server Cursors

Implemented on the server but managed by API cursor

functions (OLE DB, ODBC, DB-Library)

Client Cursors Entire result set is cached on client and all cursor

operations are performed against this cached set


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Working with T-SQL Server Cursors

Declare the cursor

Populate the cursor

Retrieve (fetch) the result set

First, Next, Prior, Last, Absolute n, Relative n Optional: update or delete a row

Close the cursor

Free resources allocated to the cursor


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Control Statements Contd


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BEGIN..END

A set of TSQL statements to be executed can be enclosedin BEGIN..END.

Syntax:

BEGIN

{ statement | statement_block}

END


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IF..ELSE

We can execute different

sets of SQL statements based on

specified conditions.

Syntax:IF Boolean_expression

{ sql_statement | statement_block}

[ ELSE{ sql_statement |

statement_block } ]


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Example


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WHILE construct

We can execute a SQL statement or a

block of statements based on some condition.

Syntax:

WHILE Boolean_expression

{ statement | statement_block}

[ BREAK ]

{ statement | statement_block

}

[ CONTINUE ]


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Example

USE pubsGOWHILE (SELECT AVG(price) FROM titles) < $30BEGIN

UPDATE titlesSET price = price * 2

SELECT MAX(price) FROM titlesIF (SELECT MAX(price) FROM titles) > $50

BREAK

ELSECONTINUE

ENDPRINT 'Too much for the market to bear'


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GOTO keyword

GOTO:

We can change the flow of execution to a specified location (label).The statements after GOTO keyword are skipped and the

execution process continues at the specified label in the GOTOstatement.

Syntax:

GOTO label


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RETURN

RETURN: We can use RETURN at any point to exit from a block,procedure. Statements after the RETURN statement are notexecuted.

Syntax:

RETURN [ integer_expression ]


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CASE statement

Allowing to return a value based on whether anexpression is true.

Can be used wherever an expression is allowed.

Syntax:CASE expression

WHEN expression1 THEN expression1[[WHEN expression2 THEN expression2] []][ELSE expression]

END

Ex

ample:SELECT au_fname, au_lname,CASE state

WHEN 'OR' THEN 'Oregon'

END AS StateName FROMauthors


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Multi column updates using CASE

UPDATE publishersSET state =CASE

WHEN country "USA"THEN "--"

ELSE stateEND,city =CASE

WHEN pub_id = "9999"THEN "LYON"ELSE city

ENDWHERE country "USA" ORpub_id = "9999"

Two or more

columns canbe updatedusing onecommand inthis manner


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Math Functions

AVG()

MIN()

MAX() SUM()

COUNT()

SQUARE()

SQRT()

ROUND()


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String Functions

ASCII()

CHAR()

UPPE

R() LOWER()

LEN()

LTRIM()

RTRIM()

LEFT()

RIGHT()


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Time Functions

GETDATE()

DATEPART(YY,getdate())

DATEDIFF(X,Y,Z) DAY()

MONTH()

YEAR()


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System Functions

DB_ID([database_name])

DB_NAME([database_id])

HOST_ID()

HOST_NAME() ISNULL(expr,value)

OBJECT_ID(obj_name)

OBJECT_NAME(object_id)

SUSE

R_SID([login_name])

SUSER_ID([login_name])

SUSER_SNAME([server_user_id])

SUSER_NAME([server_user_id])

USER_ID([user_name])

USER_NAME([user_id])


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Outline




Control statements





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Modifying a Stored Procedure

ALTER PROCEDURE GetSubjectsASSELECT *FROM dbo.Subject;


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Deleting a Stored Procedure

DROP PROCEDURE dbo.GetSubjects


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Executing a Stored Procedure

Local stored procedures

Execute

Remote stored procedures

Execute

or

OpenQuery(linked server name,exec stored procedure)

Example

Execute dbo.GetSubjects


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Outline




Control statements





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User-Defined Function

A function returning value

Advantages:

better performance, higher productivity, ease of use, increasedscalability for database application

embed complex logic within a query.

create new functions for complex expressions.

Three distinct types

Scalar functions that return a single value Updateable inline table functions similar to views

Multi-statement table functions that build a result set with code


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Creating a Scalar Function


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Creating a Inline Table Function


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Modifying a Scalar Function


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Summary

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Documents

Session6_SP_UDF