Solved

check if a value exists in a column

Posted on 2011-03-23
4
210 Views
Last Modified: 2012-06-22
I want to check if a value exist in a column:
I'm very new to SQL and c#.
I suspect that there is some easier way to do this.
Right now i do this
SqlCommand myCommand2 = new SqlCommand("SELECT count(*) FROM Customers WHERE CustNo =" + customerNumber, conn);
                int count = (int)myCommand2.ExecuteScalar();
                if (count == 1)
                {
                    existing = true;
                }
                else
                {
                    existing = false;
                }
return existing;

Open in new window

0
Comment
Question by:llegar100
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 28

Expert Comment

by:Ryan McCauley
ID: 35197066
I'd do it like this:

SqlCommand myCommand2 = new SqlCommand("SELECT count(*) FROM Customers WHERE CustNo = @CustomerNumber", conn);

myCommand2.Parameters.AddWithValue("@CustomerNumber", customerNumber) 

return (boolean)myCommand2.ExecuteScalar();

Open in new window


First, parameterize your customerNumber - it protects you from SQL Injection attacks, and it's quicker for the query engine to parse.

Second, the result of your query will either be zero or something else, so you can convert it directly to a boolean value without doing your if statements - if it's zero, the boolean is zero, and if it's anything else, the boolean returns true (non-zero).
0
 
LVL 1

Expert Comment

by:Muralidharand
ID: 35197243

Please parameterize your query .

SqlCommand myCommand2 = new SqlCommand("SELECT count(*) FROM Customers WHERE CustNo = @CustomerNumber", conn);

myCommand2.Parameters.AddWithValue("@CustomerNumber", customerNumber)

return Convert.ToBoolead(myCommand2.ExecuteScalar());

0
 
LVL 13

Expert Comment

by:dwkor
ID: 35200409
Use the following SQL instead. you don't need to count actual rows to check existence
select case when exists (SELECT count(*) FROM Customers WHERE CustNo = @CustomerNumber) then 1 else 0 end

Open in new window

0
 
LVL 28

Accepted Solution

by:
Ryan McCauley earned 500 total points
ID: 35210614
You probably meant this:

select case when exists (SELECT CustNo FROM Customers WHERE CustNo = @CustomerNumber) then 1 else 0 end

Open in new window


For some reason, I never think to use the EXISTS statement, but it's great - SQL will run until it finds a match and then quit - there's no need to get a count of rows here when you don't care about the count at all, just a yes/no.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

In this article I will describe the Copy Database Wizard method as one possible migration process and I will add the extra tasks needed for an upgrade when and where is applied so it will cover all.
Ever needed a SQL 2008 Database replicated/mirrored/log shipped on another server but you can't take the downtime inflicted by initial snapshot or disconnect while T-logs are restored or mirror applied? You can use SQL Server Initialize from Backup…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an antispam), the admini…
Are you ready to implement Active Directory best practices without reading 300+ pages? You're in luck. In this webinar hosted by Skyport Systems, you gain insight into Microsoft's latest comprehensive guide, with tips on the best and easiest way…

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question