Pl Sql Error Handling Exception
For example: NO_DATA_FOUND and ZERO_DIVIDE are called Named System exceptions. Informational: Messages for conditions that do not have an effect on performance or correctness, but that you might want to change to make the code more maintainable, such as dead code Associate the name with the error code of the internally defined exception. Normally, just the failed SQL statement is rolled back, not the whole transaction. http://iipseconline.com/pl-sql/pl-sql-error-exception-handling.html
If an error occurs, and that error is handled at any level by the time we're back at the SQL*Plus prompt, we only rollback to the immediate savepoint at the start Examples of internally defined exceptions are ORA-00060 (deadlock detected while waiting for resource) and ORA-27102 (out of memory). Passing a zero to SQLERRM always returns the message normal, successful completion. Otherwise, DECODE returns the price-to-earnings ratio. read this post here
Pl Sql Exception Handling Examples
With exceptions, you can handle errors conveniently without the need to code multiple checks, as follows: BEGIN SELECT ... If a subprogram exits with an unhandled exception, then actual parameters for OUT and IN OUT formal parameters passed by value (the default) retain the values that they had before the Example 11-6 Anonymous Block Handles ZERO_DIVIDE DECLARE stock_price NUMBER := 9.73; net_earnings NUMBER := 0; pe_ratio NUMBER; BEGIN pe_ratio := stock_price / net_earnings; -- raises ZERO_DIVIDE exception DBMS_OUTPUT.PUT_LINE('Price/earnings ratio = ' Predefined PL/SQL Exceptions An internal exception is raised implicitly whenever your PL/SQL program violates an Oracle rule or exceeds a system-dependent limit.
Each handler consists of a WHEN clause, which specifies an exception, followed by a sequence of statements to be executed when that exception is raised. To reraise an exception, simply place a RAISE statement in the local handler, as shown in the following example: DECLARE out_of_balance EXCEPTION; BEGIN ... In that case, we change the value that needs to be unique and continue with the next loop iteration. Functions For Error Trapping Are Contained In Which Section Of A Pl/sql Block Have your exception handlers output debugging information.
Internal exceptions are raised implicitly (automatically) by the run-time system. Examples of internally defined exceptions include division by zero and out of memory. By associating the exception code to a name and using it as a named exception. Execution of the handler is complete, so the sub-block terminates, and execution continues with the INSERT statement.
Sometimes you can use error-checking code to avoid raising an exception, as in Example 11-7. Pl/sql Raises An Exception In Which Two Of The Following Cases For example, when an open host cursor variable is passed to a stored subprogram, the return types of the actual and formal parameters must be compatible. Handling Exceptions Raised in Handlers Only one exception at a time can be active in the exception-handling part of a block or subprogram. PL/SQL supports programmers to catch such conditions using EXCEPTION block in the program and an appropriate action is taken against the error condition.
How Can A User Defined Exception Be Raised
It is possible to declare your own exceptions for application specific errors, or associate them with Oracle "ORA-" messages that are executed using the RAISE statement. PROGRAM_ERROR 06501 -6501 It is raised when PL/SQL has an internal problem. Pl Sql Exception Handling Examples Enclosing block: Row inserted. Pl Sql Exception Handling Continue Loop Redeclaring predefined exceptions is error prone because your local declaration overrides the global declaration.
If the transaction succeeds, commit, then exit from the loop. news Many times developers will write and test code with unrealistic data, only to find the code that was working perfectly in a development environment works badly in a production environment. VALUE_ERROR 06502 -6502 It is raised when an arithmetic, conversion, truncation, or size-constraint error occurs. It is nice to think that the design will be perfected before application development starts, but in reality this seldom seems to be the case. Pl Sql Exception Handling Best Practices
Examples of bad input data are incorrect or null actual parameters and queries that return no rows or more rows than you expect. We use advertisements to support this website and fund the development of new content. You can, however, declare the same exception in two different blocks. have a peek at these guys Expect that at some time, your code will be passed incorrect or null parameters, that your queries will return no rows or more rows than you expect.
For example, the following declaration raises an exception because the constant credit_limit cannot store numbers larger than 999: DECLARE credit_limit CONSTANT NUMBER(3) := 5000; -- raises an exception BEGIN ... Exception Part Can Be Defined Twice In Same Block For each exception handler, carefully decide whether to have it commit the transaction, roll it back, or let it continue. STORAGE_ERROR PL/SQL runs out of memory or memory has been corrupted.
Using the DBMS_WARNING Package If you are writing a development environment that compiles PL/SQL subprograms, you can control PL/SQL warning messages by calling subprograms in the DBMS_WARNING package.
DBMS_OUTPUT.PUT('Try #' || i); BEGIN -- sub-block begins SAVEPOINT start_transaction; -- transaction begins DELETE FROM results WHERE res_answer = 'NO'; INSERT INTO results (res_name, res_answer) VALUES (name, answer); -- Nonunique name For example, you might define an exception named insufficient_funds to flag overdrawn bank accounts. Otherwise we rollback to the top-level 'virtual' savepoint currently in existence, which is my offending unnamed block. In Which Section Are Exception Raised From there on, the exception propagates normally.
You can place RAISE statements for a given exception anywhere within the scope of that exception. If we try to delete a product_id from the product table when it has child records in order_id table an exception will be thrown with oracle code number -2292. Use error-checking code wherever bad input data can cause an error. check my blog Scope Rules for PL/SQL Exceptions You cannot declare an exception twice in the same block.
Since there is no customer with ID value 8 in our database, the program raises the run-time exception NO_DATA_FOUND, which is captured in EXCEPTION block. Place the statement in its own sub-block with its own exception handlers. To handle raised exceptions, you write separate routines called exception handlers. Tim Hall, Oracle ACE of the year, 2006.You can buy the book for only $23.95 (30%-off) when you buy directly from the publisher, and you also get instant access to the
Pre-defined Exceptions PL/SQL provides many pre-defined exceptions, which are executed when any database rule is violated by a program. RAISE_APPLICATION_ERROR is part of package DBMS_STANDARD, and as with package STANDARD, you do not need to qualify references to it. These statements complete execution of the block or subprogram; control does not return to where the exception was raised. If you need to know which statement failed, you can use a locator variable: DECLARE stmt INTEGER; name VARCHAR2(100); BEGIN stmt := 1; -- designates 1st SELECT statement SELECT table_name INTO
INVALID_CURSOR Your program attempts an illegal cursor operation such as closing an unopened cursor. Errors are especially likely during arithmetic calculations, string manipulation, and database operations.