Tip

Returning a unique value that may or may not exist

Suppose you want to return a value from a unique record in the database, but the record's existence is not known to you. The simple way is to do SELECT COUNT, and if the count > 0 then select the value.

I suggest another way:

Suppose, for example, you want to get the salary of employee code 100 in table EMP. Employee 100 may exist or may not exist in the database. In case he or she does not exist, -1 should be returned.

  SELECT NVL(MIN(SALARY),-1)
  FROM EMP 
  WHERE EMP_CODE = 100

That will do it. If EMP exists, the value will be returned. If not, MIN function will give NULL that will be converted to -1 by the NVL. MIN does not cost because it's used on one row only.

.

For More Information

  • What do you think about this tip? E-mail us at

    Requires Free Membership to View


This was first published in June 2001

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to:

Disclaimer: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.