qr code generator vb.net source Inside Microsoft SQL Server 2008: T-SQL Programming in .NET

Encoder QR Code ISO/IEC18004 in .NET Inside Microsoft SQL Server 2008: T-SQL Programming

Inside Microsoft SQL Server 2008: T-SQL Programming
Denso QR Bar Code Generation In VS .NET
Using Barcode generation for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
www.OnBarcode.com
Creating Bar Code In .NET Framework
Using Barcode creation for ASP.NET Control to generate, create barcode image in ASP.NET applications.
www.OnBarcode.com
So it s a good practice to always construct the code in a variable, where such limitations don t apply, and then provide the variable name as input to the EXEC command, as shown here:
Painting QR Code 2d Barcode In C#
Using Barcode maker for VS .NET Control to generate, create QR Code image in VS .NET applications.
www.OnBarcode.com
QR Code ISO/IEC18004 Printer In .NET Framework
Using Barcode creation for VS .NET Control to generate, create QR image in .NET applications.
www.OnBarcode.com
DECLARE @sql AS VARCHAR(500) = 'SELECT orderid FROM dbo.Orders' + CAST(YEAR(CURRENT_TIMESTAMP) AS CHAR(4)) + ';'; EXEC(@sql);
Encode QR-Code In VB.NET
Using Barcode maker for VS .NET Control to generate, create QR Code image in .NET framework applications.
www.OnBarcode.com
Encode UCC - 12 In VS .NET
Using Barcode creation for ASP.NET Control to generate, create EAN / UCC - 13 image in ASP.NET applications.
www.OnBarcode.com
This code executes successfully .
Matrix Barcode Drawer In VS .NET
Using Barcode creator for ASP.NET Control to generate, create 2D Barcode image in ASP.NET applications.
www.OnBarcode.com
Paint PDF 417 In VS .NET
Using Barcode generation for ASP.NET Control to generate, create PDF 417 image in ASP.NET applications.
www.OnBarcode.com
EXEC Has No Interface
Encode DataMatrix In VS .NET
Using Barcode drawer for ASP.NET Control to generate, create Data Matrix 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Drawing Bar Code In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create bar code image in ASP.NET applications.
www.OnBarcode.com
As I mentioned earlier, EXEC(<string>) has no interface . Its only input is a character string with the code that you want to invoke . Remember that a dynamic batch has no access to local variables defined in the calling batch . For example, the following code attempts to access a variable defined in the calling batch and fails:
Linear 1D Barcode Printer In .NET
Using Barcode printer for ASP.NET Control to generate, create Linear image in ASP.NET applications.
www.OnBarcode.com
Encode UPCE In .NET
Using Barcode creation for ASP.NET Control to generate, create UPC-E Supplement 5 image in ASP.NET applications.
www.OnBarcode.com
USE InsideTSQL2008; DECLARE @lastname AS NVARCHAR(40) = N'Davis'; DECLARE @sql AS NVARCHAR(500) = N'SELECT empid, firstname, lastname FROM HR.Employees WHERE lastname = @lastname;'; EXEC(@sql);
Scanning UPC - 13 In VB.NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Draw PDF 417 In Java
Using Barcode encoder for Android Control to generate, create PDF417 image in Android applications.
www.OnBarcode.com
This code produces the following error:
UPC - 13 Generator In Java
Using Barcode maker for Android Control to generate, create European Article Number 13 image in Android applications.
www.OnBarcode.com
Creating Bar Code In Java
Using Barcode printer for Java Control to generate, create bar code image in Java applications.
www.OnBarcode.com
Msg 137, Level 15, State 2, Line 3 Must declare the scalar variable "@lastname".
Reading ECC200 In VB.NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Recognize PDF-417 2d Barcode In C#.NET
Using Barcode reader for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Using EXEC, if you want to access the variable, you have to concatenate its contents to the code string you re constructing dynamically:
ECC200 Maker In None
Using Barcode generation for Word Control to generate, create Data Matrix image in Microsoft Word applications.
www.OnBarcode.com
EAN-13 Maker In Visual Studio .NET
Using Barcode drawer for Reporting Service Control to generate, create GTIN - 13 image in Reporting Service applications.
www.OnBarcode.com
DECLARE @lastname AS NVARCHAR(40) = N'Davis'; DECLARE @sql AS NVARCHAR(500) = N'SELECT empid, firstname, lastname FROM HR.Employees WHERE lastname = ' + QUOTENAME(@lastname, N'''') + N';'; EXEC(@sql);
Concatenating the contents of a variable to a code string imposes a security risk (SQL injection) . You can take some measures to protect against SQL injection, such as limiting the size of the code string you re constructing, using the QUOTENAME function to quote your strings, and others; however, it s very hard if not impossible to completely eliminate the exposure . Of course, in practice you don t need dynamic SQL at all in such a situation . You could simply use static code and refer to @lastname in the filter, as in:
9 Dynamic SQL
DECLARE @lastname AS NVARCHAR(40) = N'Davis'; SELECT empid, firstname, lastname FROM HR.Employees WHERE lastname = @lastname;
I ve used this simple example just for demonstration purposes . Imagine that other sections of the code are constructed dynamically and cannot be used in a static query . Concatenating the contents of a variable has its performance drawbacks . SQL Server may end up creating a new ad hoc execution plan for each unique query string even though the query pattern is the same . To demonstrate this, run the following code invoking the same dynamic batch twice, with a different value in the variable in each invocation:
-- Run with Davis DECLARE @lastname AS NVARCHAR(40) = N'Davis'; DECLARE @sql AS NVARCHAR(500) = N'SELECT empid, firstname, lastname /* 65353E43-7E73-4094-84AC-D632ABB0FF7F */ FROM HR.Employees WHERE lastname = ' + QUOTENAME(@lastname, N'''') + N';'; EXEC(@sql); GO -- Run with King DECLARE @lastname AS NVARCHAR(40) = N'King'; DECLARE @sql AS NVARCHAR(500) = N'SELECT empid, firstname, lastname /* 65353E43-7E73-4094-84AC-D632ABB0FF7F */ FROM HR.Employees WHERE lastname = ' + QUOTENAME(@lastname, N'''') + N';'; EXEC(@sql); GO
I planted a GUID as a comment in the code so that it would be easy to track down the associated plans in cache . Run the following code to query the plans in cache:
SELECT cacheobjtype, objtype, usecounts, sql FROM sys.syscacheobjects WHERE sql LIKE N'%65353E43-7E73-4094-84AC-D632ABB0FF7F%' AND sql NOT LIKE N'%sys%';
This generates the following output:
cacheobjtype -------------Compiled Plan Compiled Plan objtype -------Adhoc Adhoc usecounts ---------1 1 sql -----------------------------------SELECT ... WHERE lastname = 'Davis'; SELECT ... WHERE lastname = 'King';
A separate ad hoc plan was created for each unique input . If you invoke the code again with an input that was already specified, the corresponding plan can be reused . But with many unique inputs, you can end up flooding the cache with ad hoc plans . Note that in certain
Copyright © OnBarcode.com . All rights reserved.