Working with SQL Server Date/Time Variables: Displaying Dates and Times in Different Formats

This article will explain cover discussion of date/time data by exploring how to use different SQL Server functions to display dates and times in different formats.
Depending on your environment, your needs, and/or the audience of your application, the format for displaying date and time might vary. Internationally we have many difference ways to represent a given date and/or time. Here are a few examples of different ways we might display the date January 22, 2003 with or without a time of 10:31 PM.
• 2003/01/22 10:31PM
• 2003/01/22 22:31
• 22-01-2003
• 22 January 2003
• Jan 22 2003 10:13PM
• January 22, 2003
Let's review the SQL Server functions that can be used to display these date formats, starting with the CONVERT function. The CONVERT function is provided to help with converting a DATETIME or SMALLDATETIME variables, or any other string that holds a valid date, into different date/time display formats. The CONVERT function is called using the following syntax:
CONVERT ( data_type [ ( length) ] , expression [ , style ] )
Where data_type [(length)] is the target data type format and length, expression is any valid Microsoft expression that represents the date/time you want to display, and style specifies the output format for the data/time.
Using the CONVERT function, with different styles, allows you to display date and time data in many different formats. Let's look at what I am taking about. The easiest way to demonstrate how to use the CONVERT function is to review some TSQL code that displays the current time in a few different display formats. The following script uses only the CONVERT function to display the different formats.
PRINT '1) HERE IS MON DD YYYY HH:MIAM (OR PM) FORMAT ==>' +
CONVERT(CHAR(19),GETDATE())
PRINT '2) HERE IS MM-DD-YY FORMAT ==>' +
CONVERT(CHAR(8),GETDATE(),10)
PRINT '3) HERE IS MM-DD-YYYY FORMAT ==>' +
CONVERT(CHAR(10),GETDATE(),110)
PRINT '4) HERE IS DD MON YYYY FORMAT ==>' +
CONVERT(CHAR(11),GETDATE(),106)
PRINT '5) HERE IS DD MON YY FORMAT ==>' +
CONVERT(CHAR(9),GETDATE(),6)
PRINT '6) HERE IS DD MON YYYY HH:MM:SS:MMM(24H) FORMAT ==>' +
CONVERT(CHAR(24),GETDATE(),113)
Here is the output from the above script:
1) HERE IS MON DD YYYY HH:MIAM (OR PM) FORMAT ==>Feb 5 2003 5:54AM
2) HERE IS MM-DD-YY FORMAT ==>02-05-03
3) HERE IS MM-DD-YYYY FORMAT ==>02-05-2003
4) HERE IS DD MON YYYY FORMAT ==>05 Feb 2003
5) HERE IS DD MON YY FORMAT ==>05 Feb 03
6) HERE IS DD MON YYYY HH:MM:SS:MMM(24H) FORMAT ==>05 Feb 2003 05:54:39:567
As you can see, this script displays the current date in many different formats. Some formats have two digit years, while others have four digit years. Some displays have 24 hour or AM/PM time formats. Still others have the month displayed as a numeric value, while others have a month abbreviation. Some of the displays also have the date displayed in DD MON YYYY format. I suggest you review Books Online for a description of all the formats that the CONVERT function can display using different styles.
Even though the CONVERT function has a number of data/time output styles, it still might not have the exact display format you need to display. Sometimes you will need to use other TSQL functions as well, to get the display format you desire.
Another important date/time function worth describing is DATEPART. This function will take a date/time expression and return a single part of the date, such as hour, minute, month, day, etc. A call to this function has the following form:
DATEPART(datepart, date)>
Where the datepart is one of the following: Year, yy, yyyy, quarter, qq, q, month, mm, m, dayofyear, dy, y, day, dd, d, week, wk, ww, weekday, dw,hour, hh, minute, mi, n, second, ss, s, millisecond, or ms. And date is a valid date expression. This function will return an integer representing the particular date part requested.
Let's review how the CONVERT and/or DATEPART functions can be used to display January 22, 2003 with a time of 10:31 PM to meet all of the display formats I showed at the top of this article.
Some of the formats can be created using the different "style" options on the CONVERT statement. Although a number of these formats above will not only require the CONVERT and/or DATEPART functions, but other TSQL functions like SUBSTRING, RIGHT, and CAST to build the desired display format. If you are unfamiliar with these additional functions, read Books Online for more information. To show you how to create each of these display formats I will build a simple script for each of the different formats.
The first example displays the date in 2003/01/22 10:13PM format. This can be done with the following simple script that uses the CONVERT and SUBSTRING functions. Note this example uses the 111 style format of the CONVERT function.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT CONVERT(CHAR(11),@DT,111) +
SUBSTRING(CONVERT(CHAR(19),@DT,100),13,19)
Normally there is always more than one way to get the same results. Here is another way to get the same date displayed by using the DATEPART, CAST and RIGHT functions:
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT CAST(DATEPART(YYYY,@DT) AS CHAR(4)) + '/'
+ RIGHT(CAST(100+DATEPART(MM,@DT) AS CHAR(3)),2) + '/'
+ RIGHT(CAST(100+DATEPART(DD,@DT) AS CHAR(3)),2) + ' '
+ CASE WHEN DATEPART(HH,@DT) < 13
THEN RIGHT(CAST(100+DATEPART(HH,@DT) AS CHAR(3)),2)
ELSE CAST(DATEPART(HH,@DT)-12 AS CHAR(2))
END + ':'
+ RIGHT(CAST(100+DATEPART(MI,@DT) AS CHAR(3)),2)
+ CASE WHEN DATEPART(HH,@DT) < 13
THEN 'AM'
ELSE 'PM'
END
The next example will display the date in 2003/01/22 22:31 format. This example uses the REPLACE function to convert the dashes, of CONVERT style 120, to slashes.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT REPLACE(CONVERT(CHAR(16),@DT,120),'-','/')
The following example will display the date in 22-01-2003 format, without the time portion. To display only the date portion and truncate the time part, I specified an output data type and length. In the example below a CHAR(10) was used for data type and length. This will cause the CONVERT function to display only the first 10 characters of style 105.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT CONVERT(CHAR(10),@DT,105)
The next example displays the date using 22 January 2003 format. To produce this date output, I will introduce a new function, DATENAME. The DATENAME function returns a character string representing the requested part of the date. The DATENAME function uses the following syntax:
DATENAME( datepart , date )
Where the datepart is one of the following: Year, yy, yyyy, quarter, qq, q, month, mm, m, dayofyear, dy, y, day, dd, d, week, wk, ww, weekday, dw,hour, hh, minute, mi, n, second, ss, s, millisecond, or ms, and date is a valid date expression. This function will return a character string representing the particular date part requested. Be aware that the "weekday" parm returns the day name, like Sunday, Monday, Tuesday, etc, and the "month" parm returns the month name, like January, February, March, etc. This example uses DATENAME to return the DAY, MONTH and YEAR of the variable @DT. The month portion of the date will be returned with the spelled out version of the month, or in this case "January."
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT DATENAME(DAY,@DT) + ' ' + DATENAME(MONTH,@DT) + ' ' + DATENAME(YEAR, @DT)
The CONVERT function alone allows me to output a date with Jan 22 2003 10:13PM format. By using a style of 100, the CONVERT function displays the date format needed.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT CONVERT(CHAR(19),@DT,100)
To display a date in January 22, 2003 format I will again use the DATENAME function, I just change the output formatting, by rearranging the calls for each date part.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT DATENAME(MONTH,@DT) + ' ' + DATENAME(DAY,@DT) + ', ' + DATENAME(YEAR, @DT)
Three more SQL Server functions that might help you with formatting date output are worth mentioning. These functions are DAY, MONTH, and YEAR. Each of these functions accepts a date expression, and returns an integer value representing the day, month or year depending on which function is being called. Here is an example of how these functions are used to return a date in 01/22/2003 format.
DECLARE @DT DATETIME
SET @DT = '2003-01-22 10:31 PM'
SELECT '0' + CAST(MONTH(@DT) AS CHAR(1)) + '/' + CAST(DAY(@DT) AS
CHAR(2)) + '/' + CAST(YEAR(@DT) AS CHAR(4))
Conclusion
There are many different way to display a given date and time value. Because of this, SQL Server provides the CONVERT function to format date/time values into a number of preset output formats. Also by using the CONVERT function along with one or more additional SQL Server functions, such as DATEPART you should be able to display the date any way you need.

What is Three tier Application ?

3 tier design refers to the following layers:

Presentation layer - this is the user interface end of our application, the controls, graphics, grid etc.
Application (middle) layer - this is the layer in which the business logic sit. The business logic of the application is the logic that decides if all conditions are met and that implement our use case scenarios. The bulk of the functionality of our program is found in the application layer.
Data layer - the data layer allows us to "persist" data for the application or in other words, store and retrieve the data required for the running of the application . The persistance mechanism could be a relational database, XML files, or some other means of storing data.

These 3 layers can be deployed in any number of ways depending on the situation. In a ASP.Net app, you could have the pages being the presentation layer, the stored procedures being the application layer and the Data tables being the Data layer. What is important of 3 tier is to spit the application and presentation layer (2 tier this is basically integrated). You may also decide to put the Applicaion layer in a WebService so that you may also create a Forms application that reuses the same application layer.

3 Tier design is important for three reasons:

Reuse - So that many applications can use the same logic to do some action.
Maintainability - So that it can easily be changed without effecting the other layers
Scalability - So that we can move the application layer to a more powerfull machine if we need better performance.

One last thought... Although stored procedures allow for implementation of the middle tier. This should be avoided for good design. Stored Procedures shoudl be used for Data Logic, to make sure all data stay consistant and complete in the database. One should rather implement the middle tier in a seperate code layer. This can still be part of the same ASP.Net App. You only have to make sure that all ASP.Net forms access a middle tier (class or service) and never the database directly. The middle layer must access the database for any data related operations. The same counts for Forms applications. You may decide to put this middle tier facade in the app or in a service.

SQL Server Performance Tuning Tips for Visual Basic Applications

SQL Server Performance Tuning Tips for Visual Basic Applications: "Performance Tuning Tips for Creating Visual Basic
Applications Using SQL Server "

These are some good tips for ADO / SQL Server ? Visual Basic Programming