Pl Sql Error Handler
So, the sub-block cannot reference the global exception unless it was declared in a labeled block, in which case the following syntax is valid: block_label.exception_name The following example illustrates the scope For example, in the Oracle Precompilers environment, any database changes made by a failed SQL statement or PL/SQL block are rolled back. PL/SQL procedure successfully completed. From there on, the exception propagates normally.
For example, if you declare an exception named invalid_number and then PL/SQL raises the predefined exception INVALID_NUMBER internally, a handler written for INVALID_NUMBER will not catch the internal exception. For example, here is a procedure with unnecessary code that could be removed. 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 Note: When using pragma RESTRICT_REFERENCES to assert the purity of a stored function, you cannot specify the constraints WNPS and RNPS if the function calls SQLCODE or SQLERRM. browse this site
Pl Sql Exception Handling Examples
Some common internal exceptions have predefined names, such as ZERO_DIVIDE and STORAGE_ERROR. Therefore, a PL/SQL block cannot handle an exception raised by a remote subprogram. 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.
When you see an error stack, or sequence of error messages, the one on top is the one that you can trap and handle. Exceptions declared in a block are considered local to that block and global to all its sub-blocks. An exception can be either internally defined (by the run-time system) or user-defined. Pl/sql Raises An Exception In Which Two Of The Following Cases In the following example, if the SELECT INTO statement raises ZERO_DIVIDE, you cannot resume with the INSERT statement: DECLARE pe_ratio NUMBER(3,1); BEGIN DELETE FROM stats WHERE symbol = 'XYZ'; SELECT price
If there are nested PL/SQL blocks like this. Pl Sql Exception Handling Best Practices EXCEPTION WHEN NO_DATA_FOUND THEN -- catches all 'no data found' errors Exceptions improve readability by letting you isolate error-handling routines. IF ... https://docs.oracle.com/cd/E11882_01/appdev.112/e25519/errors.htm If no exception has been raised, SQLCODE returns zero and SQLERRM returns the message: ORA-0000: normal, successful completion.
Consider the following example: BEGIN DECLARE ---------- sub-block begins past_due EXCEPTION; due_date DATE := trunc(SYSDATE) - 1; todays_date DATE := trunc(SYSDATE); BEGIN IF due_date < todays_date THEN RAISE past_due; END IF; User Defined Exception In Pl Sql THEN -- handle the error WHEN OTHERS THEN -- handle all other errors END; If you want two or more exceptions to execute the same sequence of statements, list the exception SET SERVEROUTPUT ON; DECLARE stock_price NUMBER := 9.73; net_earnings NUMBER := 0; pe_ratio NUMBER; BEGIN -- Calculation might cause division-by-zero error. The runtime system raises predefined exceptions implicitly (automatically).
Pl Sql Exception Handling Best Practices
NO_DATA_FOUND A SELECT INTO statement returns no rows, or your program references a deleted element in a nested table or an uninitialized element in an index-by table. https://docs.oracle.com/cd/E11882_01/timesten.112/e21639/exceptions.htm DECLARE huge_quantity EXCEPTION; CURSOR product_quantity is SELECT p.product_name as name, sum(o.total_units) as units FROM order_tems o, product p WHERE o.product_id = p.product_id; quantity order_tems.total_units%type; up_limit CONSTANT order_tems.total_units%type := 20; message VARCHAR2(50); Pl Sql Exception Handling Examples PL/SQL predefines some common Oracle errors as exceptions. Functions For Error Trapping Are Contained In Which Section Of A Pl/sql Block Tips for Handling PL/SQL Errors In this section, you learn three techniques that increase flexibility.
Thus, a block or subprogram can have only one OTHERS handler. An exception name declaration has this syntax: exception_name EXCEPTION; For semantic information, see "Exception Declaration". You can write handlers for predefined exceptions using the names in the following list: Exception Oracle Error SQLCODE Value ACCESS_INTO_NULL ORA-06530 -6530 CASE_NOT_FOUND ORA-06592 -6592 COLLECTION_IS_NULL ORA-06531 -6531 CURSOR_ALREADY_OPEN ORA-06511 -6511 However, the same scope rules apply to variables and exceptions. Pl Sql Continue After Exception
Topics: Declaring PL/SQL Exceptions Scope Rules for PL/SQL Exceptions Associating a PL/SQL Exception with a Number (EXCEPTION_INIT Pragma) Defining Your Own Error Messages (RAISE_APPLICATION_ERROR Procedure) Redeclaring Predefined Exceptions Declaring PL/SQL Exceptions Who said you didn't learn anything useful in primary school? For example, if your SELECT statement returns multiple rows, TimesTen returns an error (exception) at runtime. Isolating error-handling routines makes the rest of the program easier to read and understand.
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. Exception Handling In Oracle Interview Questions You code the pragma EXCEPTION_INIT in the declarative part of a PL/SQL block, subprogram, or package using the following syntax: PRAGMA EXCEPTION_INIT(exception_name, -Oracle_error_number); where exception_name is the name of a COMPILE statement, the current session setting might be used, or the original setting that was stored with the subprogram, depending on whether you include the REUSE SETTINGS clause in the statement.
You need not worry about checking for an error at every point it might occur.
The invoker does not handle the exception, so PL/SQL returns an unhandled exception error to the host environment. If the transaction fails, control transfers to the exception handler, where you roll back to the savepoint undoing any changes, then try to fix the problem. Code that can never be executed You can also treat particular messages as errors instead of warnings. How Can We Handle Errors In Pl Sql If the statement fails, Oracle rolls back to the savepoint.
TimesTen does not roll back. The developer raises the exception explicitly. Instead, you must assign their values to local variables, then use the variables in the SQL statement, as shown in the following example: DECLARE err_num NUMBER; err_msg VARCHAR2(100); BEGIN ... Finally, the example recompiles the procedure, and the compiler generates a warning about the unreachable code.
dbms_output.put_line(TO_CHAR(v_TimeStamp, 'DD-MON-YY HH24:MI:SS')); dbms_output.put(' Module: ' || p_Module); dbms_output.put(' Error #' || p_SeqNum || ': '); dbms_output.put_line(v_ErrorMsg); -- Output the call stack. You declare an exception by introducing its name, followed by the keyword EXCEPTION. For example, ORA-06500 (PL/SQL: storage error) has the predefined name STORAGE_ERROR. Again, a single exception handler can trap all division-by-zero errors, bad array subscripts, and so on.
The inner block does not have an exception handler for C, so exception C propagates to the outer block. The pragma must appear somewhere after the exception declaration in the same declarative section, as shown in the following example: DECLARE deadlock_detected EXCEPTION; PRAGMA EXCEPTION_INIT(deadlock_detected, -60); BEGIN null; -- Some operation If the optional third parameter is TRUE, the error is placed on the stack of previous errors. If there is no handler for the exception, then PL/SQL returns an unhandled exception error to the invoker or host environment, which determines the outcome (for more information, see "Unhandled Exceptions").
Therefore, the RAISE statement and the WHEN clause refer to different exceptions. WHEN others THEN exception3-handling-statements END; Example Let us write some simple code to illustrate the concept. For example, you might want to roll back a transaction in the current block, then log the error in an enclosing block. COLLECTION_IS_NULL Your program attempts to apply collection methods other than EXISTS to an uninitialized (atomically null) nested table or varray, or the program attempts to assign values to the elements of
For information about autonomous routines, see "AUTONOMOUS_TRANSACTION Pragma". You can have any number of exception handlers, and each handler can associate a list of exceptions with a sequence of statements. SQL> Catching Unhandled Exceptions Remember, if it cannot find a handler for a raised exception, PL/SQL returns an unhandled exception error to the host environment, which determines the outcome. 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 ...
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. In the following example, if the SELECT INTO statement raises ZERO_DIVIDE, you cannot resume with the INSERT statement: DECLARE pe_ratio NUMBER(3,1); BEGIN DELETE FROM stats WHERE symbol = 'XYZ'; SELECT price DECLARE name VARCHAR2(20); ans1 VARCHAR2(3); ans2 VARCHAR2(3); ans3 VARCHAR2(3); suffix NUMBER := 1; BEGIN ... Thus, the RAISE statement and the WHEN clause refer to different exceptions.
The procedure compiles without warnings.