Oracle Exception Handle 异常处理

Handling PL/SQL Errors：
http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96624/07_errs.htm

引用

Retrieving the Error Code and Error Message: SQLCODE and SQLERRM：
In an exception handler, you can use the built-in functions SQLCODE and SQLERRM to find out which error occurred and to get the associated error message. For internal exceptions, SQLCODE returns the number of the Oracle error. The number that SQLCODE returns is negative unless the Oracle error is no data found, in which case SQLCODE returns +100. SQLERRM returns the corresponding error message. The message begins with the Oracle error code.

For user-defined exceptions, SQLCODE returns +1 and SQLERRM returns the message: User-Defined Exception.

unless you used the pragma EXCEPTION_INIT to associate the exception name with an Oracle error number, in which case SQLCODE returns that error number and SQLERRM returns the corresponding error message. The maximum length of an Oracle error message is 512 characters including the error code, nested messages, and message inserts such as table and column names.

If no exception has been raised, SQLCODE returns zero and SQLERRM returns the message: ORA-0000: normal, successful completion.

You can pass an error number to SQLERRM, in which case SQLERRM returns the message associated with that error number. Make sure you pass negative error numbers to SQLERRM. In the following example, you pass positive numbers and so get unwanted results:

DECLARE
   err_msg VARCHAR2(100);
BEGIN
   /* Get all Oracle error messages. */
   FOR err_num IN 1..9999 LOOP
      err_msg := SQLERRM(err_num); -- wrong; should be -err_num
      INSERT INTO errors VALUES (err_msg);
   END LOOP;
END;

Passing a positive number to SQLERRM always returns the message user-defined exception unless you pass +100, in which case SQLERRM returns the message no data found. Passing a zero to SQLERRM always returns the message normal, successful completion.

You cannot use SQLCODE or SQLERRM directly in a SQL statement. 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
   ...
EXCEPTION
   WHEN OTHERS THEN
      err_num := SQLCODE;
      err_msg := SUBSTR(SQLERRM, 1, 100);
      INSERT INTO errors VALUES (err_num, err_msg);
END;

The string function SUBSTR ensures that a VALUE_ERROR exception (for truncation) is not raised when you assign the value of SQLERRM to err_msg. The functions SQLCODE and SQLERRM are especially useful in the OTHERS exception handler because they tell you which internal exception was raised.

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.

Oracle Exception Handling：
http://psoug.org/reference/exception_handling.html


Oracle/PLSQL Topics: Exception Handling：
http://www.techonthenet.com/oracle/exceptions/