Explain Error Handling In Pl/sql
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Churchill Run-time errors arise from design faults, coding mistakes, hardware failures, and many other sources. Although you cannot
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anticipate all possible errors, you can plan to handle certain kinds pl sql error handling when others of errors meaningful to your PL/SQL program. With many programming languages, unless you disable error checking, a
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run-time 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 pl sql error handling example you "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 exception handling in pl sql Tips for 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 se
are called exceptions. Note: The language of warning and error messages depends on the NLS_LANGUAGE parameter. For information about this parameter, see Oracle Database Globalization Support Guide. Topics Compile-Time Warnings
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Overview of Exception Handling Internally Defined Exceptions Predefined Exceptions User-Defined Exceptions Redeclared Predefined error handling transact sql Exceptions Raising Exceptions Explicitly Exception Propagation Unhandled Exceptions Error Code and Error Message Retrieval Continuing Execution After Handling Exceptions Retrying Transactions
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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 https://docs.oracle.com/cd/B10500_01/appdev.920/a96624/07_errs.htm initialization parameter specifies the current location of the trace files. You can find the value of this parameter 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 https://docs.oracle.com/cloud/latest/db112/LNPLS/errors.htm (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 performance or correctness, but you might want to change it to make the code more maintainable. Code that can never run By setting the compilation parameter PLSQL_WARNINGS, you can: Enable and disable all warnings, one or more categories of warnings, or specific warnings Treat specific warnings as errors (so that those conditions must be corrected before you can compile the PL/SQL unit) You can set the value of PLSQL_WARNINGS for: Your Oracle database instance Use the ALTER SYSTEM statement, described in Oracle Database SQL Language Reference. Your session Use the ALTER SESSION statement, described in Oracle Database SQL Language Reference. A st
| PL/SQL Exception Handling Exception Handling In this section we will discuss about the following, 1) What is Exception Handling. 2) Structure of http://plsql-tutorial.com/plsql-exception-handling.htm Exception Handling. 3) Types of Exception Handling. 1) What 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 it from exiting abruptly. When an exception occurs a messages which explains its cause is error handling recieved. PL/SQL Exception message consists of three parts. 1) Type of Exception 2) An Error Code 3) 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 pl sql error -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. 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 i