Error Handling In Pl Sql Example
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Churchill Run-time errors arise from design faults, coding mistakes, hardware failures, and many other sources. Although you cannot anticipate
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all possible errors, you can plan to handle certain kinds of pl sql exception handling in loop errors meaningful to your PL/SQL program. With many programming languages, unless you disable error checking, a run-time
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error such as stack overflow or division by zero stops normal processing and returns control to the operating system. With PL/SQL, a mechanism called exception handling lets you error handling t sql "bulletproof" your program so that it can continue operating in the presence of errors. This chapter discusses the following topics: Overview of PL/SQL Error Handling Advantages of PL/SQL Exceptions Predefined PL/SQL Exceptions Defining Your Own PL/SQL Exceptions How PL/SQL Exceptions Are Raised How PL/SQL Exceptions Propagate Reraising a PL/SQL Exception Handling Raised PL/SQL Exceptions Tips for error handling transact sql Handling PL/SQL Errors Overview of PL/SQL Error Handling In PL/SQL, a warning or error condition is called an exception. Exceptions can be internally defined (by the run-time system) or user defined. Examples of internally defined exceptions include division by zero and 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 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
are called exceptions. Note: The language of warning and error messages depends on
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the NLS_LANGUAGE parameter. For information about this parameter, see Oracle pl sql cursor exception Database Globalization Support Guide. Topics Compile-Time Warnings Overview of Exception Handling Internally Defined Exceptions Predefined Exceptions
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User-Defined Exceptions Redeclared Predefined Exceptions Raising Exceptions Explicitly Exception Propagation Unhandled Exceptions Error Code and Error Message Retrieval Continuing Execution After Handling Exceptions Retrying Transactions https://docs.oracle.com/cd/B10500_01/appdev.920/a96624/07_errs.htm After Handling Exceptions See Also: "Exception Handling in Triggers" "Handling FORALL Exceptions After FORALL Statement Completes" Tip: If you have problems creating or running PL/SQL code, check the Oracle Database trace files. The USER_DUMP_DEST initialization parameter specifies the current location of the trace files. You can find the value of this parameter https://docs.oracle.com/cloud/latest/db112/LNPLS/errors.htm by issuing SHOW PARAMETER USER_DUMP_DEST. For more information about trace files, see Oracle Database Performance Tuning Guide. Compile-Time Warnings While compiling stored PL/SQL units, the PL/SQL compiler generates warnings for conditions that are not serious enough to cause errors and prevent compilation—for example, using a deprecated PL/SQL feature. To see warnings (and errors) generated during compilation, either query the static data dictionary view *_ERRORS (described in Oracle Database Reference) or, in the SQL*Plus environment, use the command SHOW ERRORS. The message code of a PL/SQL warning has the form PLW-nnnnn. For the message codes of all PL/SQL warnings, see Oracle Database Error Messages. Table 11-1 summarizes the categories of warnings. Table 11-1 Compile-Time Warning Categories Category Description Example SEVERE Condition might cause unexpected action or wrong results. Aliasing problems with parameters PERFORMANCE Condition might cause performance problems. Passing a VARCHAR2 value to a NUMBER column in an INSERT statement INFORMATIONAL Condition does not affect
| PL/SQL Exception Handling Exception Handling In this section we will discuss about the following, 1) What is Exception Handling. 2) Structure of Exception Handling. 3) Types of Exception Handling. 1) What http://plsql-tutorial.com/plsql-exception-handling.htm is Exception Handling? PL/SQL provides a feature to handle the Exceptions which occur in a PL/SQL Block known as exception Handling. Using Exception Handling we can test the code and avoid http://www.plsqltutorial.com/plsql-exception/ it from exiting abruptly. When an exception occurs a messages which explains its cause is recieved. PL/SQL Exception message consists of three parts. 1) Type of Exception 2) An Error Code 3) pl sql A message By Handling the exceptions we can ensure a PL/SQL block does not exit abruptly. 2) Structure of Exception Handling. General Syntax for coding the exception section DECLARE Declaration section BEGIN Exception section EXCEPTION WHEN ex_name1 THEN -Error handling statements WHEN ex_name2 THEN -Error handling statements WHEN Others THEN -Error handling statements END; General PL/SQL statments can be used in the Exception Block. pl sql exception When an exception is raised, Oracle searches for an appropriate exception handler in the exception section. For example in the above example, if the error raised is 'ex_name1 ', then the error is handled according to the statements under it. Since, it is not possible to determine all the possible runtime errors during testing fo the code, the 'WHEN Others' exception is used to manage the exceptions that are not explicitly handled. Only one exception can be raised in a Block and the control does not return to the Execution Section after the error is handled. If there are nested PL/SQL blocks like this. DELCARE Declaration section BEGIN DECLARE Declaration section BEGIN Execution section EXCEPTION Exception section END; EXCEPTION Exception section END; In the above case, if the exception is raised in the inner block it should be handled in the exception block of the inner PL/SQL block else the control moves to the Exception block of the next upper PL/SQL Block. If none of the blocks handle the exception the program ends abruptly with an error. 3) Types of Exception. There are 3 types of Exc
own exception and raise it in your code. Introducing to PL/SQL Exception In PL/SQL, any kind of errors is treated as exceptions. An exception is defined as a special condition that change the program execution flow. The PL/SQL provides you with a flexible and powerful way to handle such exceptions. PL/SQL catches and handles exceptions by using exception handler architecture. Whenever an exception occurs, it is raised. The current PL/SQL block execution halts and control is passed to a separate section called exception section. In the exception section, you can check what kind of exception has been occurred and handle it appropriately. This exception handler architecture enables separating the business logic and exception handling code hence make the program easier to read and maintain. PL/SQL Exception There are two types of exceptions: System exception: the system exception is raised by PL/SQL run-time when it detect an error. For example, NO_DATA_FOUND exception is raised if you select a non-existing record from the database. Programmer-defined exception: the programmer-defined exception is defined by you in a specific application. You can map exception names with specific Oracle errors using the EXCEPTION_INIT pragma. You can also assign a number and description to the exception using RAISE_APPLICATION_ERROR. Defining PL/SQL Exception An exception must be defined before it can be raised. Oracle provides many predefined exceptions in the STANDARD package. To define an exception you use EXCEPTION keyword as below: EXCEPTION_NAME EXCEPTION; 1 EXCEPTION_NAME EXCEPTION; To raise exception that you've defined you use the RAISE statement as follows: RAISE EXCEPTION_NAME; 1 RAISE EXCEPTION_NAME; In the exception handler section, you use can handle the exception as usual. The following example illustrates the programmer-defined exceptions. We get the salary of an employee and check it with the job's salary range. If the salary is below the range, we raise an exception BELOW_SALARY_RANGE. If the salary is above the range, we raise the exception ABOVE_SALARY_RANGE just make it simple for demonstration. SET SERVEROUTPUT ON SIZE 100000; DECLARE -- define exceptions BELOW_SALARY_RANGE EXCEPTION; ABOVE_SALARY_RANGE EXCEPTION; -- salary variables n_salary empl