barcode generator in vb.net codeproject Working with Functions and Value Expressions in Software

Painting Code 3/9 in Software Working with Functions and Value Expressions

Working with Functions and Value Expressions
Scanning Code-39 In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
USS Code 39 Encoder In None
Using Barcode maker for Software Control to generate, create Code-39 image in Software applications.
Using the MAX and MIN Functions
Recognize ANSI/AIM Code 39 In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
Code 39 Extended Encoder In Visual C#
Using Barcode generation for Visual Studio .NET Control to generate, create Code 39 image in Visual Studio .NET applications.
The MAX and MIN functions are so similar that it is worth discussing them together. The MAX function returns the highest value from the specified column, and the MIN function returns the lowest value. Both functions require that you specify a column name. For example, suppose you want to return the highest value from the NUMBER_SOLD column in the ARTIST_CDS table. Your SELECT statement would look like the following:
Encode Code 3/9 In VS .NET
Using Barcode printer for ASP.NET Control to generate, create Code 3/9 image in ASP.NET applications.
Draw Code 3/9 In Visual Studio .NET
Using Barcode generation for .NET framework Control to generate, create USS Code 39 image in Visual Studio .NET applications.
SELECT MAX(NUMBER_SOLD) AS MAX_SOLD FROM ARTIST_CDS;
Draw Code 39 Extended In VB.NET
Using Barcode maker for .NET Control to generate, create Code 39 image in VS .NET applications.
Barcode Creation In None
Using Barcode drawer for Software Control to generate, create bar code image in Software applications.
When you execute this statement, your query results will include only one value (one row and one column), as shown in the following results:
Drawing EAN-13 In None
Using Barcode encoder for Software Control to generate, create European Article Number 13 image in Software applications.
Making EAN / UCC - 14 In None
Using Barcode encoder for Software Control to generate, create USS-128 image in Software applications.
MAX_SOLD ------54
Printing USS Code 128 In None
Using Barcode maker for Software Control to generate, create Code 128 Code Set C image in Software applications.
UPC-A Supplement 5 Drawer In None
Using Barcode creator for Software Control to generate, create UPC-A Supplement 2 image in Software applications.
This result, by itself, is not particularly helpful. It would be nice if your query results also included the name of the artist and the CD. However, SQL does not support a SELECT statement such as the following:
Print USPS PLANET Barcode In None
Using Barcode generator for Software Control to generate, create USPS Confirm Service Barcode image in Software applications.
EAN / UCC - 13 Drawer In Visual Basic .NET
Using Barcode maker for Visual Studio .NET Control to generate, create EAN / UCC - 13 image in .NET applications.
SELECT ARTIST_NAME, CD_NAME, MAX(NUMBER_SOLD) FROM ARTIST_CDS;
Encoding Code 3 Of 9 In Java
Using Barcode encoder for Java Control to generate, create Code39 image in Java applications.
2D Barcode Printer In Visual Studio .NET
Using Barcode creator for VS .NET Control to generate, create 2D Barcode image in VS .NET applications.
Because set functions treat data as groups, you cannot specify the artist name and CD name without somehow grouping the data together. As it stands now, the MAX function treats the entire table as one group; however, neither the ARTIST_NAME values nor the CD_NAME values are grouped together in any way, so the SELECT clause becomes illogical. Whenever you include a set function in an SQL statement, then every argument in the SELECT list must either be a set function or be included in a group (using the GROUP BY clause described a little later in this topic). One way around this is to use a subquery in the WHERE clause to return the maximum value and then return the necessary information based on that value, as shown in the following example:
GS1 128 Creator In Objective-C
Using Barcode generator for iPad Control to generate, create UCC-128 image in iPad applications.
Read Barcode In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
SELECT ARTIST_NAME, CD_NAME, NUMBER_SOLD FROM ARTIST_CDS WHERE NUMBER_SOLD = ( SELECT MAX(NUMBER_SOLD) FROM ARTIST_CDS );
Code 128B Drawer In None
Using Barcode generator for Online Control to generate, create Code 128A image in Online applications.
Decoding Barcode In Visual Studio .NET
Using Barcode Control SDK for ASP.NET Control to generate, create, read, scan barcode image in ASP.NET applications.
The subquery finds the maximum value (54) and uses that value as a condition in the WHERE clause. The NUMBER_SOLD value must equal 54 as long as that is the highest NUMBER_SOLD value in the table. Once you define the necessary search condition in the WHERE clause, you can then use these results to return the information you need. If you execute this statement, one row is returned:
ARTIST_NAME -----------Patsy Cline: CD_NAME ---------------------------Patsy Cline 12 Greatest Hits NUMBER_SOLD ----------54
SQL: A Beginner s Guide
As you can see, you now have all the information you need to determine which artist and CD have sold the greatest number. As I said earlier, the MAX and MIN functions are very similar. If you replace MIN for MAX in the previous example, your query results will look like the following:
ARTIST_NAME ---------------William Ackerman CD_NAME ---------Past Light NUMBER_SOLD ----------12
The Past Light row is returned because that is the row with the lowest NUMBER_SOLD value. The MAX and MIN functions are not limited to numeric data. You can also use them to compare character strings. For example, suppose you want to know which artist comes first alphabetically. The following statement will return B.B. King:
SELECT MIN(ARTIST_NAME) AS LOW_NAME FROM ARTIST_CDS;
If you use the MAX function, the statement will return William Ackerman.
NOTE
It is quite likely that the tables in your database will separate first names from last names because this is a more flexible design. I ve included both names in one column to provide you with simple examples of how various statements work. If names were separated into two columns, the MIN or MAX function would need to be used with the appropriate column.
Now let s back up a little and return to the idea of grouping data. As I mentioned, a set function treats a table as one group if no grouping has been implemented. However, you can easily use a GROUP BY clause to group data. Suppose you want to know the maximum amount sold by each artist. You can group data based on the ARTIST_NAME values:
SELECT FROM WHERE GROUP ARTIST_NAME, MAX(NUMBER_SOLD) AS MAX_SOLD ARTIST_CDS NUMBER_SOLD > 30 BY ARTIST_NAME;
The WHERE clause returns only those rows with a NUMBER_SOLD value greater than 30. These rows are then grouped together according to the ARTIST_NAME values. Once they re grouped together, the maximum amount is returned for each artist, as shown in the following query results:
ARTIST_NAME ------------Bing Crosby Joni Mitchell Patsy Cline MAX_SOLD -------34 45 54
10:
Copyright © OnBarcode.com . All rights reserved.