asp.net mvc qr code generator Important in Visual Studio .NET

Printer QR-Code in Visual Studio .NET Important

Important
QR Code JIS X 0510 Maker In .NET
Using Barcode maker for VS .NET Control to generate, create QR Code image in .NET applications.
www.OnBarcode.com
QR Code Reader In VS .NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
You cannot play with the ON clause's order any way you'd like. There's a certain relationship that must be maintained between the order of the specified tables and the order of the specified ON clauses for the query to be valid. The relationship is called a chiastic relationship. A chiastic relationship is neither unique to SQL nor to computer science; rather, it appears in many fields, including poetry, linguistics, mathematics, and others. In an ordered series of items, this relationship correlates the first item with the last, the second with the next to last, and so on. For example, the word ABBA has a chiastic relationship between the letters. As an example for a chiastic relationship in mathematics, recall the arithmetic sequence I described in the last chapter: 1, 2, 3, ..., n. To calculate the sum of the elements, you make n/2 pairs based on a chiastic relationship (1 + n, 2 + n 1, 3 + n 2, and so on). The sum of each pair is always 1 + n; therefore, the total sum of the arithmetic sequence is (1 + n) * n / 2 = (n + n2) / 2. Similarly, the relationship between the tables specified in the FROM clause and the ON clauses must be chiastic for the query to be valid. That is, the first ON clause can refer only to the immediate two tables right above it. The second ON clause can refer to the previously referenced tables and to an additional one right above them, and so on. Figure 5-5 illustrates the chiastic relationship maintained in the last query. The code in the figure was slightly rearranged for readability.
Encoding Bar Code In .NET
Using Barcode printer for Visual Studio .NET Control to generate, create barcode image in .NET framework applications.
www.OnBarcode.com
Bar Code Reader In .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Figure 5-5. Chiastic relationship in a multi-join query
QR Code JIS X 0510 Printer In C#
Using Barcode generator for .NET Control to generate, create QR Code image in VS .NET applications.
www.OnBarcode.com
QR Code Creation In VS .NET
Using Barcode printer for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
www.OnBarcode.com
Without using parentheses, the queries are not very readable and you need to be aware of the chiastic relationship in order to write a valid query. Conversely, if you do use parentheses, the queries are more readable and intuitive and you don't need to concern yourself with chiastic relationships, as parentheses force you to write correctly.
Draw QR Code ISO/IEC18004 In Visual Basic .NET
Using Barcode printer for .NET Control to generate, create QR Code JIS X 0510 image in .NET framework applications.
www.OnBarcode.com
EAN13 Drawer In .NET Framework
Using Barcode drawer for Visual Studio .NET Control to generate, create EAN / UCC - 13 image in VS .NET applications.
www.OnBarcode.com
Semi Joins
Matrix Barcode Drawer In VS .NET
Using Barcode printer for .NET Control to generate, create Matrix 2D Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Generating UCC.EAN - 128 In .NET Framework
Using Barcode generation for Visual Studio .NET Control to generate, create GS1-128 image in VS .NET applications.
www.OnBarcode.com
Semi joins are joins that return rows from one table based on the existence of related rows in the other table. If you return attributes from the left table, the join is called a left semi join. If you return attributes from the right table, it's called a right semi join. There are several ways to achieve a semi join: using inner joins, subqueries, and set operations (which I'll demonstrate later in the chapter). Using an inner join, you select attributes from only one of the tables and apply DISTINCT. For example, the following query returns customers from Spain that made orders: SELECT DISTINCT C.CustomerID, C.CompanyName FROM dbo.Customers AS C JOIN dbo.Orders AS O ON O.CustomerID = C.CustomerID WHERE Country = N'Spain';
Encoding 1D Barcode In Visual Studio .NET
Using Barcode encoder for .NET Control to generate, create 1D image in VS .NET applications.
www.OnBarcode.com
Drawing UCC - 14 In VS .NET
Using Barcode maker for VS .NET Control to generate, create EAN - 14 image in .NET applications.
www.OnBarcode.com
You can also use the EXISTS predicate as follows: SELECT CustomerID, CompanyName FROM dbo.Customers AS C WHERE Country = N'Spain' AND EXISTS (SELECT * FROM dbo.Orders AS O WHERE O.CustomerID = C.CustomerID);
Printing European Article Number 13 In C#.NET
Using Barcode generator for VS .NET Control to generate, create GS1 - 13 image in .NET applications.
www.OnBarcode.com
Draw Bar Code In Java
Using Barcode generator for BIRT reports Control to generate, create bar code image in BIRT reports applications.
www.OnBarcode.com
If you're wondering whether there's any performance difference between the two, in this case the optimizer generates an identical plan for both. This plan is shown in Figure 5-6.
Barcode Drawer In None
Using Barcode creation for Software Control to generate, create barcode image in Software applications.
www.OnBarcode.com
UPC Code Printer In None
Using Barcode creator for Microsoft Excel Control to generate, create GTIN - 12 image in Office Excel applications.
www.OnBarcode.com
Figure 5-6. Execution plan for a left semi join
Quick Response Code Generator In None
Using Barcode generator for Software Control to generate, create QR Code image in Software applications.
www.OnBarcode.com
GS1 - 13 Generation In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create GS1 - 13 image in ASP.NET applications.
www.OnBarcode.com
[View full size image]
Making Code 128 In Objective-C
Using Barcode drawer for iPhone Control to generate, create Code-128 image in iPhone applications.
www.OnBarcode.com
Read QR Code In C#
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
The inverse of a semi join is an antisemi join, where you're looking for rows in one table based on their nonexistence in the other. You can achieve an antisemi join (left or right) using an outer join, filtering only outer rows. For example, the following query returns customers from Spain that made no orders. The anti-semi join is achieved using an outer join: SELECT C.CustomerID, C.CompanyName FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O ON O.CustomerID = C.CustomerID WHERE Country = N'Spain' AND O.CustomerID IS NULL;
You can also use the NOT EXISTS predicate as follows: SELECT CustomerID, CompanyName FROM dbo.Customers AS C WHERE Country = N'Spain' AND NOT EXISTS (SELECT * FROM dbo.Orders AS O WHERE O.CustomerID = C.CustomerID);
As you can see in the execution plans shown in Figure 5-7 for the two query variations, the solution using the NOT EXISTS predicate performs better.
Copyright © OnBarcode.com . All rights reserved.