Oracle 11g Pl Sql Error Handling
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program to continue to operate in the presence of errors. Topics: Overview of PL/SQL Run-Time Error Handling Guidelines for Avoiding and Handling PL/SQL Errors and pl sql exception handling examples Exceptions Advantages of PL/SQL Exceptions Predefined PL/SQL Exceptions Defining Your Own PL/SQL user defined exception in pl sql Exceptions How PL/SQL Exceptions Are Raised How PL/SQL Exceptions Propagate Reraising a PL/SQL Exception Handling Raised PL/SQL Exceptions pl sql exception handling best practices Overview of PL/SQL Compile-Time Warnings Overview of PL/SQL Run-Time Error Handling In PL/SQL, an error condition is called an exception. An exception can be either internally defined (by the run-time pl sql exception when others system) or user-defined. Examples of internally defined exceptions are ORA-22056 (value string is divided by zero) and ORA-27102 (out of memory). Some common internal exceptions have predefined names, such as ZERO_DIVIDE and STORAGE_ERROR. The other internal exceptions can be given names. You can define your own exceptions in the declarative part of any PL/SQL block, subprogram, or package. For example,
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you might define an exception named insufficient_funds to flag overdrawn bank accounts. User-defined exceptions must be given names. When an error occurs, an exception is raised. That is, normal execution stops and control transfers to the exception-handling part of your PL/SQL block or subprogram. Internal exceptions are raised implicitly (automatically) by the run-time system. User-defined exceptions must be raised explicitly by RAISE statements or invocations of the procedure DBMS_STANDARD.RAISE_APPLICATION_ERROR. To handle raised exceptions, you write separate routines called exception handlers. After an exception handler runs, the current block stops executing and the enclosing block resumes with the next statement. If there is no enclosing block, control returns to the host environment. For information about managing errors when using BULK COLLECT, see Handling FORALL Exceptions (%BULK_EXCEPTIONS Attribute). Example 11-1 calculates a price-to-earnings ratio for a company. If the company has zero earnings, the division operation raises the predefined exception ZERO_DIVIDE, the execution of the block is interrupted, and control is transferred to the exception handlers. The optional OTHERS handler catches all exceptions that the block does not name specifically. Example
to your PL/SQL program. With many programming languages, unless you disable error checking, a run-time error such as stack overflow or division by zero stops normal
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processing and returns control to the operating system. With PL/SQL, a mechanism exception no data found oracle called exception handling lets you bulletproof your program so that it can continue operating in the presence of errors. functions for error trapping are contained in which section of a pl/sql block This chapter contains these topics: Overview of PL/SQL Runtime Error Handling Advantages of PL/SQL Exceptions Summary of Predefined PL/SQL Exceptions Defining Your Own PL/SQL Exceptions How PL/SQL Exceptions Are Raised https://docs.oracle.com/cd/B28359_01/appdev.111/b28370/errors.htm How PL/SQL Exceptions Propagate Reraising a PL/SQL Exception Handling Raised PL/SQL Exceptions Overview of PL/SQL Compile-Time Warnings Overview of PL/SQL Runtime Error Handling In PL/SQL, an error condition is called an exception. Exceptions can be internally defined (by the runtime system) or user defined. Examples of internally defined exceptions include division by zero and out of memory. Some common internal exceptions https://docs.oracle.com/cd/B19306_01/appdev.102/b14261/errors.htm have predefined names, such as ZERO_DIVIDE and STORAGE_ERROR. The other internal exceptions can be given names. You can define exceptions of your own in the declarative part of any PL/SQL block, subprogram, or package. For example, you might define an exception named insufficient_funds to flag overdrawn bank accounts. Unlike internal exceptions, user-defined exceptions must be given names. When an error occurs, an exception is raised. That is, normal execution stops and control transfers to the exception-handling part of your PL/SQL block or subprogram. Internal exceptions are raised implicitly (automatically) by the run-time system. User-defined exceptions must be raised explicitly by RAISE statements, which can also raise predefined exceptions. To handle raised exceptions, you write separate routines called exception handlers. After an exception handler runs, the current block stops executing and the enclosing block resumes with the next statement. If there is no enclosing block, control returns to the host environment. For information on managing errors when using BULK COLLECT, see "Handling FORALL Exceptions with the %BULK_EXCEPTIONS Attribute". Example 10-1 calculates a price-to-earnings ratio for a company. If the company has zero
March 2012 Oracle Magazine Online 2016 2015 2014 2013 2012 2011 2010 January 2012 March 2012 May 2012 July 2012 September 2012 November 2012 As Published In March/April 2012 TECHNOLOGY: PL/SQL Error Management http://www.oracle.com/technetwork/issue-archive/2012/12-mar/o22plsql-1518275.html By Steven Feuerstein Part 6 in a series of articles on understanding http://allthingsoracle.com/error-handling/ and using PL/SQL Even if you write absolutely perfect PL/SQL programs, it is possible and even likely that something will go wrong and an error will occur when those programs are run. How your code responds to and deals with that error often spells the difference between a successful application and one that pl sql creates all sorts of problems for users as well as developers. This article explores the world of error management in PL/SQL: the different types of exceptions you may encounter; when, why, and how exceptions are raised; how to define your own exceptions; how you can handle exceptions when they occur; and how you can report information about problems back to your users. Exception Overview There are three pl sql exception categories of exceptions in the world of PL/SQL: internally defined, predefined, and user-defined. An internally defined exception is one that is raised internally by an Oracle Database process; this kind of exception always has an error code but does not have a name unless it is assigned one by PL/SQL or your own code. An example of an internally defined exception is ORA-00060 (deadlock detected while waiting for resource). A predefined exception is an internally defined exception that is assigned a name by PL/SQL. Most predefined exceptions are defined in the STANDARD package (a package provided by Oracle Database that defines many common programming elements of the PL/SQL language) and are among the most commonly encountered exceptions. One example is ORA-00001, which is assigned the name DUP_VAL_ON_INDEX in PL/SQL and is raised when a unique index constraint is violated. A user-defined exception is one you have declared in the declaration section of a program unit. User-defined exceptions can be associated with an internally defined exception (that is, you can give a name to an otherwise unnamed exception) or with an application-specific error. Every exception has an error code and an error message associated with it. Oracle Database provides fu
you should consider them as your closest friends. They are the ones that honestly say what is wrong with your program. We cannot foresee all possible problematic events, and even the best programmers write bugs. Exceptions There are three kinds of exceptions Internally defined: A system error, defined by Oracle, that occurs. Predefined: The most common internally defined exceptions that are given predefined names. User defined: A logical error which you define and raise yourself System errors could occur from improper coding, like the “ORA-01001: Invalid cursor”, which you should try to fix as soon as possible in your code. And the “TOO_MANY_ROWS”-error might give you clues about bad data quality. To resolve these bugs, it is important to know where, when and why it happened. But system errors could also occur from hardware failures, like the “ORA-12541: TNS: no listener”, when an ftp-server might be unreachable over the network. In that case, all you can do, and should do, is provide proper error handling and transaction management, and give as detailed information as possible about this situation to the people that need to know. These system-errors always have an error number assigned, so you can easily identify the error. The 22 predefined exceptions also have a name assigned, which allows for easier, and more readable exception handling. For the other, non-predefined, system-errors, a name can be linked by using the pragma “EXCEPTION_INIT”. DECLARE network_error EXCEPTION; PRAGMA EXCEPTION_INIT(network_error, -12541); BEGIN ... EXCEPTION WHEN too_many_rows THEN ... WHEN network_error THEN ... END; User defined errors we will raise ourselves. They can be given a number and a name. To raise a user defined error with a chosen number and error message, we call the procedure “RAISE_APPLICATION_ERROR”. Oracle allows us the create error numbers in the range of -20000 to -20999. This allows us to create 1000 unique error codes for our logical errors throughout our application. Just like we did for system errors, we can name our user defined errors by using the pragma “EXCEPTION_INIT”. BEGIN RAISE_APPLICATION_ERROR(-20000,’Logical error occured’); END; If we do not care about the error code and er