What is Flag

Anil Kumar

15y2.5k

Hi,
I am having doubt in flag. plz tell me what is the use of flag in .net and SQL Serevr and why we used it??

8 Replies

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Sam Hobbs15y ago
If you are asking about flags in general, I don't use them as much as many people do. There are many uses for flags and I use them for many things.

In a database, you could call most boolean fields flags. So a flag could mean Active or Inactive. You could use a one-character field to hold one of many characters (letters) to indicate something. You could use byte fields in the manner that the Wikipedia article describes to contain bit flags that indicate various conditions.

You could use a flag in a loop to indicate things that can result in termination of the loop. A flag could indicate end-of-data and anohter flag could indicate that a certain condition has been met.

You could use a flag as an instance variable that indicates a condition that various members need to use. For example a flag could be used to indicate that an object has been opened.

The word flag in this context is very general.
Vilas Gite15y ago
@Anil Kumar..

How to set trace flag in Sql Server?

Please refer:

http://plataan.typepad.com/microsoftdynamics/2007/11/how-to-set-trac.html

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Anil Kumar15y ago
Yes. Danis.

But i have a question that when we should use Flags in our application??
Sam Hobbs15y ago
Is the term "flag" used by SQL anywhere other than in the term "Trace Flags"? The term flag can be used in many ways so you need to get the definition specific to each context. I updated the Wikipedia article because the article was misleading by saying that a flag is always bit fields. A flag also can be other data types; there is no clear definiton that applies to programmming generally. So in the context of SQL you need to know how SQL defines the word and when I did a quick search of "sql flags" in the MSDN the only results I see is for Trace Flags. Is there any other use of the word that you are not sure of?
Dinesh Beniwal15y ago
Anil query resolved?
Jiteendra Sampathirao15y ago
Nice thread..

Thans vulpes..very Informative.....
Vilas Gite15y ago
HI Anil,
just see:

http://social.msdn.microsoft.com/Forums/en/sqldataaccess/thread/9cb0327e-7fcc-4110-a7c6-c6411e78e36a

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Vulpes15y ago
A 'flag' is essentially a value which has a certain meaning and there's generally at least two related flags.

See Wikipedia (http://en.wikipedia.org/wiki/Flag_(computing)) for a fuller definition.

In .NET, there's a type of enum which is decorated with the [Flags] attribute where the members have values which are powers of two.

This allows you to combine values and, when you print them out, the runtime is able to figure out the constituents. For example:

using System;

[Flags]
enum Sides
{
Left = 1,
Right = 2,
Top = 4,
Bottom = 8
}

class Test
{
static void Main()
{
Sides s = Sides.Left | Sides.Bottom;
Console.WriteLine(s); // Left, Bottom
Console.ReadKey();
}
}

SQL Server has 'trace flags' (see http://msdn.microsoft.com/en-us/library/ms188396.aspx).