ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Oracle PL/SQL Exceptions

Updated on March 18, 2012

Exceptions in Oracle are powerful error handling mechanism. Do you feel little difficulty hearing the word Exception handling? This page depicts Exception handling and gives you very clear understanding of error handling in Oracle PL/SQL. I have also explored some myths about exception which often confuses us.

Why & when exception handling are needed?

The errors occurred during the execution of a PL/SQL is called run time error. In general, run time errors are abnormal & crucial which causes your pl/sql program or task uncompleted. So, in general or by standards, it was a good practice to anticapte them and record a log of them. This is where the role of exceptions comes in your pl/sql.

Exception

Exception in Oracle are the error handling section. When ever there is a run time error occurs in your pl/sql code, the execution jumps to your exception block.

Exception section in your pl/sql code should be inside your BEGIN section and placed above END. Below is the syntax of a PL./SQL block using exception.

DECLARE
    ...........
BEGIN
   ...........
EXCEPTION
     WHEN exception_name THEN
         ................
END;
 
 
Where exception_name is oracle defined and below are few examples.
NO_DATA_FOUND - Occurred when a SELCT INTO returns no rows.
VALUE _ERROR  - Occurred when a value assigned is more than 
                defined size or of different datatype.
 

Refer below example, the pl/sql code terminates abnormally wihout a exception block.

declare 
   v_char varchar2(5) ; 
begin 
   v_char := 'Sample Text'; 
   dbms_output.put_line(v_char); 
end; 
 
Error report: 
ORA-06502: PL/SQL: numeric or value error: character string buffer
too small ORA-06512: at line 4 
06502. 00000 - "PL/SQL: numeric or value error%s"

Refer below example, when ever a exception occurs, pl/sql code is completing with a trapped message instead of terminating abnormally.

declare 
   v_char varchar2(5) ; 
begin 
   v_char := 'Sample Text'; 
   dbms_output.put_line(v_char); 
EXCEPTION 
   WHEN VALUE_ERROR THEN 
     dbms_output.put_line('Hi There! 
                       The value supplied is too large!'); 
end;
 
anonymous block completed 
Hi There! The value supplied is too large!

Some myths about Exception

Exception works only for the code after BEGIN. If there are any erros in DECLARE section of your code, it will not be handled by exception. Refer below example.

declare
  v_char varchar2(5) := 'Sample Text';
begin
  dbms_output.put_line(v_char);
Exception
  when no_data_found then
     dbms_output.put_line('Inside no_data_found:' || sqlerrm);
  when value_error then
     dbms_output.put_line('Inside value_error:' || sqlerrm);
  when others then
     dbms_output.put_line('Inside others_found:' || sqlerrm);end;
Error report:

ORA-06502: PL/SQL: numeric or value error: character string buffer too small ORA-06512: at line 2

06502. 00000 - "PL/SQL: numeric or value error%s"

I would suggest writing variable initialiization separately is a best practice. Refer below example which would make sense instead of the above code.

declare 
   v_char varchar2(5);-- := 'Sample Text'; 
begin 
 
   v_char := 'Sample Text'; 
   dbms_output.put_line(v_char);
 
Exception 
   when no_data_found then 
      dbms_output.put_line('Inside no_data_found:' || sqlerrm); 
when value_error then 
dbms_output.put_line('Inside value_error:' || sqlerrm); 
when others then 
dbms_output.put_line('Inside others_found:' || sqlerrm); 
end;
 
anonymous block completed 

Inside value_error:ORA-06502: PL/SQL: numeric or value error: character string buffer too small

Expect more topics on user defined exception and more interesting facts on exceptions with my hub.

Common Mistakes in PL/SQL

Comments

    0 of 8192 characters used
    Post Comment

    • selvirajan profile imageAUTHOR

      selvirajan 

      2 years ago from India

      Thanks for encouraging.

    • profile image

      M.A.Anwar 

      8 years ago

      Examples are great. Exception handling in oracle is strong and you have shown it.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)