programming sql server 2005

8/8/2019 Programming SQL Server 2005

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Programming SQL ServerDatabase


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Objectives

Writing basic Transact SQL Block

Learn the programming constructs

Assign values to variables

Control-of flow statements

Working with dynamic SQLRAISERROR statement


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Writing Transact SQL Blocks

Basic Transact SQL Block

Declare

Begin

Begin Try

--Stmts

End Try

Begin Catch--Exception handling code

End Catch

End


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Assign Values to variables

Declaring variables

Declare @ DataType

Cannot initialize variables during declaration

Example

Declare @t int

Assign Values to variables

Use select keyword

Example

Select @t = 10

Select @t = max(basic) from employee

Use set keyword

Example


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Control-Of-Flow statements

GoTo StatementsIF (SELECT SYSTEM_USER()) = 'payroll

GOTO calculate_salary

--other statements

calculate_salary:

-- Statements to calculate a salary would appear

--after the label

IF StatementIF (@ErrorSaveVariable 0)

BEGIN

PRINT 'Errors encountered, rolling back.

ROLLBACK

END

ELSE

BEGIN

PRINT 'No Errors encountered, committing.

COMMIT

END


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Control-Of-Flow statements

Case Construct

Syntax :

Case Variable / column

When Value1 Then statements

When value2 then statements

elsestatements

end

SELECT job = CASE Job

WHEN RBM THEN

Regional Business Manager

WHEN BA THENBusiness Analyst

ELSE

Trainees

END FROM Employee ORDER BY Job


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Control-of-flow statements

While Statement

While Begin

StatementsEnd

Example

DECLARE abc CURSOR FORSELECT * FROM Shippers

OPEN abc

FETCH NEXT FROM abc

WHILE (@@FETCH_STATUS = 0)

FETCH NEXT FROM abc

CLOSE abc

DEALLOCATE abc


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Return statement

Unconditionally terminates a query, stored procedure, or batch.

None of the statements in a stored procedure or batch following the RETURN statement are

executed.

When used in a stored procedure can specify an integer value to return to the calling

application, batch, or procedure.

If no value is specified on RETURN, a stored procedure returns the value 0.


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CREATE PROCEDURE SampleProcedure @EmployeeIDParm INT, @MaxQuantity

INT OUTPUT AS

DECLARE @ErrorSave INT

SET @ErrorSave = 0

SELECT FirstName, LastName, Title FROM Employees

WHERE EmployeeID = @EmployeeIDParm

SELECT @MaxQuantity = MAX(Quantity)

FROM [Order Details]

IF (@@ERROR 0)

SET @ErrorSave = @@ERROR

RETURN @ErrorSave


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The WAITFOR statement suspends the execution of a connection until either:

A specified time interval has passed.

A specified time of day is reached.

The WAITFOR statement is specified with one of two clauses:

amount_of_time_to_pass before

Time to wait can be up to 24 hours.

ExampleWAITFOR DELAY '00:00:02'

SELECT EmployeeID FROM Northwind.dbo.Employees

Time_to_execute

which specifies completion of the WAITFOR statement

ExampleWAITFOR TIME '22:00'DBCC CHECKALLOC


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RAISERROR

Returns a user-defined error message and sets a system flag to record thatan error has occurred.

Syntax

RAISERROR ( { msg_id | msg_str } { , severity ,

state } [ , argument [ ,...n ] ] )

Example

RAISERROR ('The level for job_id:%d should be between %dand %d.', 16, 1, @@JOB_ID, @@MIN_LVL, @@MAX_LVL)


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SQL Server 2005 Cursors


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Working with Cursors

Declaring a Cursor

Declare cursorname cursor

Opening a cursor

Open cursorName

Fetching rows from the cursor

Fetch first | next | last | prior from cursor [ into variables ]

Closing a cursor

Close cursorName

Deallocating a cursor

Deallocate cursorName


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DECLARE cursor_name CURSOR[ LOCAL | GLOBAL ][ FORWARD_ONLY | SCROLL ][ STATIC | KEYSET | DYNAMIC | FAST_FORWARD ][ READ_ONLY ]FOR select_statement

[ FOR UPDATE [ OF column_name [ ,...n ] ] ]Local

Scope of the cursor is local to that batch or stored procedure

Global

Scope of the cursor is global to the connection

FORWARD_ONLYSpecifies that FETCH NEXT only can be specified


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STATIC

Cursor makes a temporary copy of the database data in temporary tables in

tempdb

KEYSET

Updates and deletes made by other users are visible

Inserts made into the table is not visible

DYNAMIC

Changes are visible as the user scrolls through the cursor

FAST_FORWARD

Declares a FORWARD_ONLY and READ_ONLY cursor


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READ_ONLY

Creates a read only cursor

Opening a cursor

Open CursorName

Fetching rows from a cursor

Fetch First | Next | Last | Prior | Absolute N from CursorName into

@v1, @v2

Closing a Cursor

Close CursorName


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CURSOR_ROWS

Total number of rows fetched by the cursor

Example


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@@FETCH_STATUS

Returns the status of the fetched row

0 success

-1 fetch statement failes

-2 row fetched is missing


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cursors

sp_cursor_list

Returns a list of cursors currently visible on the connection and their attributes.

sp_describe_cursor

Describes the attributes of a cursor, such as whether it is a forward-only or

scrolling cursor.

sp_describe_cursor_columns

Describes the attributes of the columns in the cursor result set.

sp_describe_cursor_tables

Describes the base tables accessed by the cursor.


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Sp_cursor_list

-- Declare a cursor

DECLARE abc CURSOR for select * from employee_5

OPEN abc

-- Declare a cursor variable to hold the cursor output variable

-- from sp_cursor_list.

DECLARE @Report CURSOR

-- Execute sp_cursor_list into the cursor variable.

EXEC master.dbo.sp_cursor_list @cursor_return = @Report

OUTPUT,@cursor_scope = 2

-- Fetch all the rows from the sp_cursor_list output cursor.

FETCH NEXT from @Report

WHILE (@@FETCH_STATUS -1)

BEGINFETCH NEXT from @Report

END

-- Close and deallocate the cursor from sp_cursor_list.

CLOSE @Report

DEALLOCATE @Report


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Sp_describe_cursor_columns

-- Declare and open a global cursor.

DECLARE abc CURSOR KEYSET FOR SELECT ename from employee_5

OPEN abc


EXEC master.dbo.sp_describe_cursor_columns

@cursor_return = @Report OUTPUT,

@cursor_source = N'global', @cursor_identity = N'abcFETCH NEXT from @Report

WHILE (@@FETCH_STATUS =0)

BEGIN


END

-- Close and deallocate the cursor from sp_describe_cursor_columns.

CLOSE @ReportDEALLOCATE @Report

CLOSE abc

DEALLOCATE abc

GO


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Sp_describe_cursor_columns

-- Declare and open a global cursor.

DECLARE abc CURSOR FOR SELECT ename from employee_5

OPEN abc


EXEC master.dbo.sp_describe_cursor_columns

@cursor_return = @Report OUTPUT,

@cursor_source = N'global', @cursor_identity = N'abcFETCH NEXT from @Report

WHILE (@@FETCH_STATUS =0)

BEGIN


END

-- Close and deallocate the cursor from sp_describe_cursor_columns.

CLOSE @ReportDEALLOCATE @Report

CLOSE abc

DEALLOCATE abc

GO


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Sp_describe_cursor_tables

DECLARE abc CURSOR KEYSET FOR SELECT * from employee_5OPEN abcDECLARE @Report CURSOREXEC master.dbo.sp_describe_cursor_tables

@cursor_return = @Report OUTPUT,@cursor_source = N'global', @cursor_identity = N'abc

FETCH NEXT from @ReportWHILE (@@FETCH_STATUS -1)BEGIN

FETCH NEXT from @ReportENDCLOSE @ReportDEALLOCATE @Report

GOCLOSE abcDEALLOCATE abcGO


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Working with static cursors

declare c1 cursor for select * from empdeclare @eno int, @ename varchaR(20), @dept intbegin

open c1fetch next from c1 into @eno, @ename, @deptselect @eno,@ename,@dept

waitfor delay '00:00:20fetch next from c1 into @eno, @ename, @deptselect @@fetch_status, @eno,@ename,@deptclose c1deallocate c1

end

Note : Run the update emp set dept=34 where eno=2 after runing the aboveblock of statements


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Working with dynamic cursors

declare c1 cursor scroll dynamic for select * from empdeclare @eno int, @ename varchaR(20), @dept intbegin

open c1fetch next from c1 into @eno, @ename, @deptselect @eno,@ename,@dept

waitfor delay '00:00:20fetch next from c1 into @eno, @ename, @deptselect @@fetch_status, @eno,@ename,@deptclose c1deallocate c1

end

Run the update emp set dept=34 where eno=2 after runing the above

block of statements


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Working with updateable cursors

declare c1 cursor scroll dynamic for select * from employee_5 for update of salarydeclare @eno int, @ename varchar(20), @sal intbegin

open c1fetch next from c1 into @eno,@ename,@salwhile @@fetch_Status=0begin

if @eno=103beginupdate employee_5 set salary=salary+200 where current of c1break

endfetch next from c1 into @eno,@ename,@salend

end

close c1deallocate c1


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Transact SQL(Procedures and Functions)


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objectives

Creating procedures

Stored procedure recompilation

Encrypting stored procedures

Return values from stored procedures


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Creating Stored procedures

Create procedure [schema.] procedure_name[;no]

(@parameter datatype [Varying ][=default] [OUT],...N)

[With Encryption | Recompile | Execute_As_Clause ]

As{ T-SQL block | External name Assembly.Class.Method }


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Create procedure

No

Is an optional number

Used to group the Stored procedure

Grouped procedure can be dropped together

Example

Create procedure OrderProc;1 As

Begin select * from orderMasterEnd

Create ProcedureOrderProc;2 As

Begin Select * from orderTrans End

Drop procedure OrderProc


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Create Procedure Options

VARYING

Specifies that the resultset is an output parameter

Applies only to cursor parameters

Example

CREATE PROCEDURE proc123 @c1 CURSOR VARYING

OUTPUT AS

BEGINSET @c1 = CURSOR FORWARD_ONLY STATIC FOR

SELECT * FROM EMPLOYEE;

OPEN @C1;

END

DECLARE @C2 CURSOR

EXEC PROC123 @C2 OUTFETCH NEXT FROM @C2


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Create procedure options

Encryption

Converts the text of the SP into obfuscated form

Output of obfuscation not directly visible in any catalog views

Option not valid for CLR procedures

Example

create procedure pass_check (@pwd varchar(20))

With encryption As

begin

- code of the SP

end


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Encryption

Example

Sp_helptext pass_check

The object comments have been encrypted.


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Create procedure Options

Recompile

Plan of the SP is not cached

Not specified for CLR procedures

To discard plans for individual queries

Use RECOMPILE as the Query hint


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External Name clause

Used to specify the name of the .NET assembly

The assembly would be referenced from a CLR procedure

Example

Create procedure p1 (@x int) as

External name Emp.Emp.GetDetails


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Getting information about procedures

View information about TSQL SPs

select * from sys.sql_modules

select definition from sys.sql_modules

where object_id=(select id from sys.sysobjects

where xtype='p'and name='myproc')

View information about dependencies

select * from sys.sql_dependencies

View information about CLR modules

select * from sys.assembly_modules


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Automatic Execution of SP

Procedures can be marked for automatic execution

Every time when SQL Server 2005 starts

Operates under the same permission as members of sysadmin fixed role

Error message generated by such SP is written to SQL Server error log


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Automatic Execution of SP

Mark a procedure for automatic execution

Sp_procOption SPName , True

UnMarks a procedure from automatic execution

Sp_procOption SPName , False


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Creating procedures (IN parameter)

Creating Procedure

Create procedure myproc(@p1 int IN)

as

declare

begin

end

Calling the procedure

Exec myproc 23


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Creating procedures (OUT parameter)

Creating procedure

Create procedure p1(@a int, @b int OUT) as

begin

set @b=@a+10

end

Calling procedure

Declare @t int

EXEC P1 20,@t OUT

Select @t


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Default values to stored procedures

Create procedure (@ type =value,) as

Example

CREATE PROCEDURE mytables ( @type char(2)=U)ASSELECT * FROM sysobjects WHERE type = @type contd.,

GO

EXECUTE mytablesEXECUTE mytables DEFAULTEXECUTE mytables P


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Creating procedures (OUT parameter)

Creating procedure

Create procedure p1(@a int, @b int OUT) as

begin

set @b=@a+10

end

Calling procedure

Declare @t int

EXEC P1 20,@t OUT

Select @t


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Default values to stored procedures

Create procedure (@ type =value,) as

Example

CREATE PROCEDURE mytables ( @type char(2)=U)ASSELECT * FROM sysobjects WHERE type = @type contd.,GOEXECUTE mytablesEXECUTE mytables DEFAULTEXECUTE mytables P


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Returning values from stored procedures

UsingOUT Parameters

Using CURSOR data type

Using return keyword


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Returning values from SPs

Create the SP

alter procedure myproc as

declare @nm varchar(20)

begin

select @nm=ename from employee_5 where eno=101

return @nm

endCall the SP

declare @x varchar(40)

execute @x=myproc


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Parameters with CURSOR data type

SP with CURSOR parameter

CREATE PROCEDURE proc123 @c1 CURSOR VARYING

OUTPUT AS

SET @c1 = CURSOR FORWARD_ONLY STATIC

FOR SELECT * FROM EMPLOYEE

OPEN @C1

GO

DECLARE @C2 CURSOR

EXEC PROC123 @C2 OUT

FETCH NEXT FROM @C2


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Parameters with CURSOR data type

Use CURSOR data types only forOUT parameters

Varying and OUTPUT clause is compulsory

Forward only CURSOR

Returns rows at and beyond the cursor position

Scrollable CURSOR

All rows returned to the calling batch

Cursor position is left at the position of the last fetch


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Creating triggers

Triggers are used to enforce constraints on the tables

Triggers are automatically called when data in inserted or updated ordeleted for a table

Sp_helptrigger view triggers for a table

Sp_helptext view text of a trigger

Types of triggers

AFTER

INSTEAD OF


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Create trigger statement

Create trigger on for insert | update|deleteasdeclare---begin

statementsend


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AFTER Triggers

Apply

Only to tables

Executed after

Constraint processing

inserted and deleted tables creation

The triggering action


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INSTEAD OF Triggers

Applicability

Tables and Views

execution

Before: Constraint processing

In place of: The triggering action

After: inserted and deleted tables creation


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Triggers

Types of triggers

After Triggers

InsteadOf Triggers


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After triggers(order of Execution)

Insert into table values(1003,Hyden,14000)Insert into table values(1003,Hyden,14000)

Transaction beginsTransaction begins

Constraints are checkedConstraints are checked

New Record

New Record


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After Trigger (Order of execution)

Create trigger insertCreate trigger insert

on emp for insert ason emp for insert asbeginbeginselect Row insertedselect Row inserted

endend

Trigger FiresTrigger Fires

If trigger contains aIf trigger contains a rollbackrollback,,Data is not insertedData is not inserted

If trigger contains doesIf trigger contains does

not havenot have

rollbackrollback Data is insertedData is inserted

(Transaction Ends)


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Instead of triggers

create trigger ins_on_view_v1 on v1

instead of insert asdeclare @teno numeric(4), @tename varchar(20), @tdname varchar(20),@tdno numeric(3),@tsal numeric(6)begin

select @teno=eno,@tename=ename,@tdname=dname from insertedset @tdno=2set @tsal=21000

insert into employee values(@teno,@tename,@tdno,@tsal)insert into dept values(@tdno,@tdname)select '2 rows inserted...'

end


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Tables referred inside triggers

Inserted

Contains rows that were inserted

Deleted

Contains rows that were deleted

Tables can be referenced only inside triggers


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Functions

Types of functionsScalar function

Inline Table valued function

Scalar Function

Create function (@parameter type,)

returns

as

declare

begin

end


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Functions

Inline Table valued Function

Create function (@parameter type,)

returns table

[ with encryption ]

as

return

Example

CREATE FUNCTION fn (@eno int ) RETURNS table AS RETURN ( SELECT *

FROM emp WHERE empid = @eno )


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Functions

Create function check (@dt smalldatetime)returns intasdeclare

begin

end


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Functions

Create function emp_det (@ecode numeric(5))returns tableasreturn(select * from emp where eno=@ecode)

programming sql server 2005

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