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c# generate barcode The AVG Function in Font
The AVG Function Paint PDF 417 In None Using Barcode generation for Font Control to generate, create PDF417 image in Font applications. www.OnBarcode.comDrawing Data Matrix In None Using Barcode generator for Font Control to generate, create ECC200 image in Font applications. www.OnBarcode.comTo find averages, we use the AVG function. The parameter for the function that is, what goes in the parentheses (. . .) is the expression you want to average. The expression must have a numeric value. The expression could be just the name of one of the numericvalued columns or some function of a value, such as the length of a piece of text or the number of days between two dates. For example, we can find the average handicap for members of our club by averaging the values in the Handicap column, as in Listing 89. Encoding Barcode In None Using Barcode creation for Font Control to generate, create Barcode image in Font applications. www.OnBarcode.comEAN / UCC  13 Creator In None Using Barcode maker for Font Control to generate, create GS1 128 image in Font applications. www.OnBarcode.comListing 89. Return the Average Handicap SELECT AVG(Handicap) FROM Member
Draw GTIN  13 In None Using Barcode maker for Font Control to generate, create European Article Number 13 image in Font applications. www.OnBarcode.comCode 39 Extended Drawer In None Using Barcode drawer for Font Control to generate, create Code 39 Full ASCII image in Font applications. www.OnBarcode.comAs with the COUNT function, the AVG function includes only nonNull values for the handicap. We have 20 members in total, and 17 members with handicaps. If we sum all the handicaps, we get 287. The AVG function will take the total of the handicaps (287) and divide by the number of rows that have a value in the Handicap column (17). This is what we want. If we included the members without handicaps (by dividing by the total number of rows, 20), we would essentially be saying that these members have a handicap of 0 by default, which is not at all what we want in this case. It is not always so obvious whether you want the Null values considered. For example, say we have another database with a table called Student and a column called TestScore. If we enter test scores for students, and some of the students do not take the test, then we will have a Null in the TestScore column for that student. What do we mean by the average score We could take the average over all the students (divide the total score by the count of all students), which means the students who missed the test are effectively being counted as Barcode Generator In None Using Barcode printer for Font Control to generate, create Barcode image in Font applications. www.OnBarcode.comMSI Plessey Creation In None Using Barcode drawer for Font Control to generate, create MSI Plessey image in Font applications. www.OnBarcode.comC HA PTE R 8 AGGREGA TE O PE RAT IO NS
PDF417 Scanner In .NET Using Barcode recognizer for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications. www.OnBarcode.comPDF417 Generator In Java Using Barcode printer for BIRT Control to generate, create PDF 417 image in Eclipse BIRT applications. www.OnBarcode.comhaving scored 0. On the other hand, we might take the average of just those who participated in the test (divide by the number who took the test). People (especially academics!) will argue about such things. AVG(TestScore) will always give us just the average for those who took the test (which is what I personally think we want). If we want the average over all the students, including those with a Null mark (counted as 0), we can calculate the average by hand totaling the marks (using the SUM function) and dividing by the full count. This computed average is shown in Listing 810. Barcode Reader In C# Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET applications. www.OnBarcode.comGenerating UPC Code In ObjectiveC Using Barcode creation for iPad Control to generate, create UPC Code image in iPad applications. www.OnBarcode.comListing 810. Calculate an Average Where Null Values Are Counted As Zero SELECT SUM(TestMark)/COUNT(*) FROM Student Barcode Creator In Visual Basic .NET Using Barcode creation for Visual Studio .NET Control to generate, create Barcode image in .NET applications. www.OnBarcode.comData Matrix ECC200 Recognizer In Visual C#.NET Using Barcode reader for .NET Control to read, scan read, scan image in .NET applications. www.OnBarcode.comThe query in Listing 810 is preferable to entering a mark of 0 for students who missed the test. If we do that, then we can no longer distinguish students who took the test and got 0 from students who missed the test (and even academics will agree this distinction is useful). As with the COUNT function, the AVG function can also incorporate the keywords ALL and DISTINCT. Just be aware that ALL means all the nonNull values, as opposed to distinct nonNull values. It doesn t mean take an average over all the rows (including those with Nulls), as in our discussion about test scores. I find it quite hard to come up with examples of when you would want to just average over distinct values certainly none that apply to our club database. How do the different types of the fields used as a parameter to the AVG function affect the result The AVG function will accept only numeric types. We can t attempt to average FirstName or JoinDate (although we could use functions to average the length of members first names or the number of days since their join date). What result do we expect to get when we average the handicaps of our members The total of the handicaps is 287, and the number of people with handicaps is 17. If you divide these two numbers with a calculator, you get something like 16.88235. What will SQL give us That depends. When I try this in Access 2007, I get 16.88235. In SQL Server 2005, I get 16. In SQL Server (and some other implementations of SQL), the average function returns the same type as the numbers being averaged. In this case, the Handicap column is an INT type, and so AVG(Handicap) in SQL Server returns an integer. It also does an integer division (which means the result is truncated to 16 rather than rounded to 17). We do have control over how the result is calculated. If we want to get a noninteger result for our average, we can convert the Handicap value to a floatingpoint number before we do the average. To do this we can use the CONVERT function, described in 7.1 Another way to do this is just to multiply the handicap by 1.0: AVG(Handicap * 1.0). The SQL Server syntax using the CONVERT function is shown in Listing 811. Decoding Universal Product Code Version A In VB.NET Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications. www.OnBarcode.comMaking Code 128 In None Using Barcode generation for Microsoft Excel Control to generate, create USS Code 128 image in Microsoft Excel applications. www.OnBarcode.com1. Different versions of SQL will have different functions to do this. In Oracle, you might consider using the CAST function. Code 39 Extended Maker In None Using Barcode printer for Online Control to generate, create Code 39 Extended image in Online applications. www.OnBarcode.comGS1  13 Drawer In None Using Barcode printer for Microsoft Excel Control to generate, create EAN13 image in Excel applications. www.OnBarcode.comDataMatrix Encoder In ObjectiveC Using Barcode drawer for iPhone Control to generate, create Data Matrix ECC200 image in iPhone applications. www.OnBarcode.comDrawing PDF417 2d Barcode In .NET Using Barcode creator for .NET framework Control to generate, create PDF417 2d barcode image in VS .NET applications. www.OnBarcode.com 
