Oracle pre-defined exception

Oracle provides a series of predefined exceptions in the STANDARD package. They are useful tools for debugging Oracle PL/SQL programs. For most errors, the negative number is used as the error number. You can use the SQLCODE built-in function to see the error code and use SQLERRM to get an exception built-in message.

Exception	Error	When
Access_assist_null	ORA-06530	When attempting to access an uninitialized object
CASE_NOT_FOUND	ORA-06592	This exception occurs if a CASE statement without an ELSE clause is defined and no CASE statement meets runtime conditions.
COLLECTION_IS_NULL	ORA-06531	This exception occurs when the program accesses a non-initialized nested table or VARRAY.
CURSOR_ALREADY_OPEN	ORA-06511	The cursor has been opened. If you try to OPEN the cursor again, this exception occurs.
DUP_VAL_ON_INDEX	ORA-00001	This exception is thrown when you insert a duplicate value with a unique INDEX constraint (the value is determined as conflicting by the INDEX)
INVALID_CURSOR	ORA-01001	This operation is not allowed. For example, if you close a closed cursor
INVALID_NUMBER	ORA-01722	When a numeric value is assigned a non-numeric value, this exception occurs. This exception also occurs when the LIMIT clause returns a non-positive number during batch reading.
LOGIN_DENIED	ORA-01017	The program will throw this exception when logging on with the wrong user name and password.
NO_DATA_FOUND	ORA_06548	When the select into structure is used and the statement returns a NULL value, this exception occurs when you access the deleted table in the nested table or the uninitialized element in the index by table (combined array ).
NOT_LOGGED_ON	ORA-01012	When the program sends a database call, but there is no connection (usually, after the connection is actually disconnected from the session)
PROGRAM_ERROR	ORA-06501	Errors that have not been officially captured by Oracle often occur because of a large number of Object functions in the database.
ROWTYPE_MISMATCH	ORA-06504	If the cursor structure is not suitable for PL/SQL cursor variables or the actual cursor parameter is different from the cursor parameter, this exception occurs.
SELF_IS_NULL	ORA-30625	This exception occurs when a non-static member method of the object type is called (the object type instance is not initialized ).
STORAGE_ERROR	ORA-06500	This exception is thrown when the memory is not allocated enough SGA quota or is damaged.
SUBSCRIPT_BEYOND_COUNT	ORA-06533	This exception occurs when the space allocated to the nested table or VARRAY is smaller than the used subobject (similar to the java ArrayIndexOutOfBoundsException)
SUBSCRIPT_OUTSIDE_LIMIT	ORA-06532	When an invalid index value is used to access the nested table or VARRAY
SYS_INVALID_ROWID	ORA-01410	When an invalid string is converted to ROWID
TIMEOUT_ON_RESOURCE	ORA-00051	When the database cannot safely lock resources
TOO_MANY_ROWS	ORA-01422	A common error occurs when multiple rows are returned using select into and a query. This exception is also thrown if the subquery returns multiple rows and the comparison operator is equal.
USERENV_COMMITSCN_ERROR	ORA-01725	Only the USERENV ('commitscn ') function can be used as the top-level expression in the VALUES clause of the INSERT statement or as the right operand in the SET clause of the UPDATE statement.
VALUE_ERROR	ORA-06502	When a variable is assigned to another variable that cannot hold the variable
ZERO_DIVIDE	ORA-01476	This exception occurs when a number is divided by 0.

EXCEPTION can be easily captured and processed in SQL blocks (except for compilation exceptions and exceptions thrown in Declaration blocks, A good PL/SQL programming habit is to avoid assigning values to variables in declared blocks ). If the predefined exceptions above meet the requirements, you can use them. If not, you can define your own exceptions like a JAVA program and use raise exception to throw an EXCEPTION.