Help with IDENTITY colum

Question

0.00/5 (No votes)

See more:

I am working on a project that accept users input and submit it to the database,an e-mail is sent to the user confirming there registration, as unique user_id is assign to each user, which is required to successfully log in to the webpage.

I want to automatically generate an a unique value that will be sent to each user that successfully registered.

1.Any help like a demo connectionString and the command it welcome.

Thanks

Posted 4-Jan-11 9:05am

ahmedfaruk88

Updated 4-Jan-11 11:50am

Henry Minute

v2

Add a Solution

2 solutions

Solution 1

You want to create a random string to use as a unique user name?

This has been answered here:
How to Generate Random String in C#?[^]

I think a great way to secure a unique id string without extra hit on the db is to retrieve the primary key as an integer, add a salt, and hash it to create a user name.

Posted 4-Jan-11 9:22am

wizardzz

Updated 4-Jan-11 10:52am

v2

Comments

Keith Barrow 4-Jan-11 16:38pm

This is a poor method, each check would required a database hit which is costly, but there *are* good reasons to use a random ID rather than a generated int. See http://www.codinghorror.com/blog/2007/03/primary-keys-ids-versus-guids.html

Keith Barrow 4-Jan-11 16:39pm

You can generate a new GUID on insert in SQL Server using
select newid()
Uniqueness isn't guaranteed, but the likelihood of two identical GUIDs is vanishingly small.

wizardzz 4-Jan-11 16:51pm

I would stay away from the coding horror of primary keys as id at all costs. The GUID does not guarantee uniqueness so the perf hit may be necessary. Check the updated answer.

Keith Barrow 4-Jan-11 17:00pm

A) I disagree that Identity fields are a coding horror, they've worked fine for most people in the past, but I prefer natural keys anyway.

Keith Barrow 4-Jan-11 17:07pm

B) The chances of two GUIDs being identical is astronomically low, there are 2 ^ 128 guids available, so you need the order of a quadrillion *existing* guids to make it remotely likely two would collide.

Keith Barrow 4-Jan-11 17:08pm

So I'd suggest that the database hit for checking uniqueness isn't worth it. Using GUIDs for PKs is common enough, and large projects do use it (though as I said, I'd always pefer natural keys).

wizardzz 4-Jan-11 17:27pm

Just curious, why are you posting each sentence as a new comment?

Anyway, sometimes, as in the case of high volume trading, a small unique key is worth the one time perf hit. Also GUID's tend to have a rather long character string, which can weigh down the payload or header of packets on a network. So depending on the use of the ID, a randomly generated, checked for unique ID could be preferred.

Keith Barrow 4-Jan-11 17:34pm

Just curious, why are you posting each sentence as a new comment?
If I post anything more than three full lines of text, at least on my screen res it fails, I think there is an upper char limit and I'm avoiding it. (Typed stuff is lost in my experience)

Keith Barrow 4-Jan-11 17:35pm

Also GUID's tend to have a rather long character string, which can weigh down the payload or header of packets on a network.
Depends on the context, whether this is really an issue, but I agree this is a consideration.

wizardzz 4-Jan-11 17:52pm

No problem, I am the same way regarding code blocks in comments. I need to be able to see all of it at once.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Keith Barrow · Accepted Answer · 2011-01-04T09:29:00

We can't supply a connection string, it is pretty much unique to your database (in terms of type, server, default table and security.
This[^] is the website I use for all things connection string related.

As for creating the unique identifier, you should do this in the database table rather than code if possible. When you define the primary key you should define it as an identity column[^].

Once you've inserted the user, the generated key is available by calling the ScopeIdentityMethod(): This[^] has some good examples.