Category: Mfc odbc example

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Mfc odbc example

An OCCI environment provides application modes and user-specified memory management functions. Example illustrates how to create an OCCI environment.


All OCCI objects created with the create xxx methods connections, connection pools, statements must be explicitly terminated. When appropriate, you must also explicitly terminate the environment. Example shows how you terminate an OCCI environment. If the application requires access to objects in the global scope, such as static or global variables, these objects must be set to NULL before the environment is terminated. In the preceding example, if b was a global variable, a b.

You can use the mode parameter of the createEnvironment method to specify that your application:. The Environment class is the factory class for creating Connection objects. You first create an Environment instance, and then use it to enable users to connect to the database through the crea teConnection method.

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Example creates an environment instance and then uses it to create a database connection for a database user HR with the appropriate password. You must use the termin ateConnection method shown in the following code example to explicitly close the connection at the end of the working session.

In addition, the OCCI environment should be explicitly terminated. You should remember that all objects Ref s, Bfile s, Producer s, Consumer s, and so on created or named within a Connection instance must be within the inner scope of that instance; the scope of these objects must be explicitly terminated before the Connection is terminated.

Example demonstrates how to terminate the connection and the environment. The multitenant architecture enables an Oracle database to contain a portable collection of schemas, schema objects, and nonschema objects that appear to an Oracle client as a separate database. This section discusses how to use the connection pooling feature of OCCI. The information covered includes the following topics:. The primary difference between the two is that StatelessConnectionPool s are used for applications that do not depend on state considerations; these applications can benefit from performance improvements available through use of pre-authenticated connections.

For many middle-tier applications, connections to the database should be enabled for a large number of threads. Because each thread exists for a relatively short time, opening a connection to the database for every thread would be inefficient use of connections, and would result in poor performance.

By employing the connection pooling feature, your application can create a small set of connections available to a large number of threads, enabling you to use database resources very efficiently.

To create a connection pool, you use the createConnectionPool method, as demonstrated in Example When the maximum number of connections are open in the connection pool, and all the connections are busy, an OCCI method call that needs a connection waits until it gets one, unless setErrorOnBusy was called on the connection pool.

This increment is implemented only when the total number of open connections is less than the maximum number of connections that can be opened in that connection pool. You can also configure all these attributes dynamically.

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This lets you design an application that has the flexibility of reading the current load number of open connections and number of busy connections and tune these attributes appropriately. In addition, you can use the setTimeOut method to time out the connections that are idle for more than the specified time.

The OCCI terminates idle connections periodically to maintain an optimum number of open connections. There is no restriction that one environment must have only one connection pool.

There can be multiple connection pools in a single OCCI environment, and these can connect to the same or different databases.You can join data from different areas or worksheets.

Phil Factor shows how, and warns of some of the pitfalls. It is quicker than automating Excel and you can do it without requiring a copy of Excel.

It is neater than SSIS too, and more versatile.

The MFC ODBC Classes -- CRecordset and CDatabase

The most important thing, though, is that you can aggregate before you send the data. This article will aim to show how this is done. I always feel slightly awkward in talking about ODBC. It is a Once and Future technology, developed before its time, but now showing its value for processing large volumes of data, despite its quirks, poor documentation and lackluster support.

Worksheets, or areas within worksheets, become tables. This means that you need pull far less data into SQL because you can do a lot of selection and pre-processing before the data gets anywhere near SQL server.

When you have a large number of big spreadsheets to insert as a chore, then speed matters. ODBC was conceived as a way of making it as easy to connect to a particular datasource such a relational database, text file, data document e. XMLweb-based data or spreadsheet. These drivers enable you to access a range of data files via SQL as if they were a relational database.

If you are using bit PowerShellas most of us are, then you need to use the bit version of the drivers.

mfc odbc example

All three or four if you include Visual Studio must be 64 bit. See this for the full frustrating story. More commonly, you can specify with a delimited worksheet name followed by a range, the range being a specification of the area of the worksheet just sufficient to enable the driver to find the data you want. If you leave out the range spec entirely, the entire worksheet becomes the table.

mfc odbc example

If you do this, then there is no limit to the length of the table so you can insert as many rows as you like. The ODBC provider adds new rows to the existing rows in the defined area as space allows.

Now, before we start doing interesting things with the ACE drivers, I ought to explain a bit about their connection strings. These contain the specification of the ODBC driver you wish to use, and the settings that you wish to transmit to the driver.

Using Database in your MFC program - A beginner's experience

Ignoring, for the time being, the extended property settings, For Microsoft Office Access data, set the Connection String to. Because the defaults can be changed globally in the registry, it is rather better to specify these extended properties rather than to rely on the defaults. They are not always reliable and are poorly documented by Microsoft. The driver needs to know if the first row of the table holds the name of the column. It will actually just use the first 64 characters of the header.

It does so by testing a number of rows before doing the import, and you can specify how many rows it tests before deciding the data type of the column by using MaxScanRows in the extended properties.

By default the value of this is 8. You can specify any value from 1 — 16 for 1 to 16 rows. You can also make the value to 0 so that it searches all existing rows before deciding the data type, but this slows things down. If the two types are equally mixed in the column, the provider chooses numeric over text, and you lose all the text. Also, it will judge the length of the character datatype in the column from the first rows and if the first rows are less than characters long it will truncate all the subsequent data to characters even if cell values below are longer.

You can force mixed data to be converted to text, but only when it finds mixed values on the rows that it checks. However, this will lock the entire workbook from access until you close the connection. It will do all this as well.

Latest ODBC Articles

Here is the simplest working demo I can write without blushing. One statement only can be used in the commandText.U CanCode Software focuses on general application software development. We provide complete solution for developers. Our product had been used by hundreds of top companies around the world! Free you from not daring to use components because of unable to master the key technology of components! Examples of this are ad-hoc query and reporting tools.

In both cases, the end user is allowed to build their own SQL from a list of tables. But, how can you do this when you don't know what the resulting data will look like when you write your application? Luckily ODBC provides several functions that can be used for this very purpose. After connecting to the data source, the next steps needed would be the following: 1.

For each row in the result set, allocate memory for the data depending on the C type. Did I say "luckily"? Actually, I said it with tongue firmly planted in cheek.

Examples of how to use the CODBCDynamic class While this article also includes a full-fledged test application, it's always nice to be able to see what you're getting before you invest the time in downloading, unzipping and running someone else's code. That's it! The map is keyed by the column name retrieved automatically and the data is in the form of a CDBVariantEx object. Howeveryou never have to worry about such technicalities.

Therefore, as easy as it is to iterate through all the returned the data, you can just as easily request specific columns by name.

mfc odbc example

Here's an example of how you would do that. That's how easy it is to interrogate any ODBC data source. Net Softwareall rights reserved. Other product and company names herein may be the trademarks of their respective owners.

Please direct your questions or comments to webmaster ucancode. Overview Download Purchase. Technical Support.This lesson shows you how to use these classes to create applications that allow you to retrieve and manipulate data stored in an external database.

Describe how to use MFC database objects to query a database from within your application code. DAO is generally used to access desktop databases and ODBC to connect to relational database servers through a named data source.

Both sets of classes are similar, and are based on a common programming model. Table 7. These classes work together to enable you to retrieve data from a data source so that the data can be displayed in a dialog-based view for browsing or updating.

The following sections explain the role of each class. Bear in mind that, because the ODBC and DAO versions of the classes are so similar, we might often discuss the classes in general terms rather than naming them specifically. We will draw your attention to significant differences between the classes where they occur.

The CDaoDatabase class usually establishes a connection to a desktop data source such as an Access database. Establishing a connection to a database is a two-stage process. You first create a database object, then call that object's Open member function. Both classes provide similar Open functions. The Open functions take arguments to allow you to specify whether the connection should be opened for exclusive or for read-only access.

ODBC from C Tutorial Part 1

The syntax for the OpenEx function is as follows:. If Windows NT authentication is not used on the data source, you can supply user and password information in the connection string. The second parameter, dwOptionsis a bitmask value that determines the mode in which the data source is opened. The default value is 0which specifies that the data source will be opened in the shared mode, with write access. Other values that can be used are combinations of those shown in Table 7.

This code shows how you might call OpenEx to open a connection to the pubs DSN, using the sa account with a password of password. CDatabase db; db.The Microsoft Foundation Class MFC library provides a set of functions, constants, data types, and classes to simplify creating applications for the Microsoft Windows operating systems.

In this tutorial, you will learn all about how to start and create windows based applications using MFC. MFC provides classes for many basic objects, such as strings, files, and collections that are used in everyday programming. It also provides classes for common Windows APIs and data structures, such as windows, controls, and device contexts. The framework also provides a solid foundation for more advanced features, such as ActiveX and document view processing.

In addition, MFC provides an application framework, including the classes that make up the application architecture hierarchy. The MFC framework is a powerful approach that lets you build upon the work of expert programmers for Windows. MFC framework has the following advantages. MFC - Overview Advertisements. Previous Page. Next Page. Previous Page Print Page.Powerful and flexible enough to create diagrams exactly the way you want them to appear. So easy to use that you will be able to prototype your application in just a few minutes.

Feature rich. Events such as click, double-click, hover, select, rubber-band select, copy, delete, resize and move are supported. Performance and Scalability. Our graphical classes are extremely lightweight objects enabling outstanding performance. Save Time and Money and gain Reliability. It is used by hundreds of the world's most quality conscious companies.

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It will saves you thousands of hours of complex coding and years of maintenance. To get my mailing labels printed I first used Crystal Reports. While this worked, I was not happy with the output of the label. There was too much seperation between fields, and trying to get them to look right was going to be a major programming project in itself.

In starting to do my own labels, I needed a font other than the default one.

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The first label starts about a half inch down from the top and a quarter of an inch over to the right. Time for some more variables. Positive x is to the right; positive y is up. One of the functions is IsPrinting.

I tried putting a while! This didn't work because pages will be printed one on top of the other. The key to keeping up with where in the database you are, and where to start printing is current page.

mfc odbc example

Why 30? Adjust if you only have two accross. You will also have to determine how many pages you have to print. Because there might be more labels left over than can print on a sheet, you do a mod on the number records. This will tell you if there are any remaining on a partial sheet, if so, add one to the page count.Tom Archer explains how to use the Microsoft Text Driver and the.

Hence, these simple class wrappers. The article, demo project, and source code were updated. Direct usage of ODBC is very complex. Anybody who tries to work with ODBC will agree with this statement.

Have you ever tried to issue multiple direct ODBC calls only to have some of the calls after the first fail? The authors of this library have combined the flexibility of templates with the power of ODBC to create a truly unique and robust library for database access!!

Discover the concept of late binding—the work behind the scenes to realize the late binding mechanism. Sample code and examples are provided. Discover the most common uses of the Process class to launch separate processes programs in a variety of ways.

Example code is in C and VB. By Manoj Debnath. Learn the basics here. By Mark Henri. By Nick E. By Dale Harkness. Visual Basic Today. By Hannes DuPreez. Programming Insights. By Tapas Pal. Today This Week All-Time.

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