PLSQL :NEW and :OLD

referencing new as new old as old in oracle trigger
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Can anyone help me understand when to use :NEW and :OLD in PLSQL blocks, I'm finding it very difficult to understand their usage.

You normally use the terms in a trigger using :old to reference the old value and :new to reference the new value.

Here is an example from the Oracle documentation linked to above

CREATE OR REPLACE TRIGGER Print_salary_changes
  BEFORE DELETE OR INSERT OR UPDATE ON Emp_tab
  FOR EACH ROW
WHEN (new.Empno > 0)
DECLARE
    sal_diff number;
BEGIN
    sal_diff  := :new.sal  - :old.sal;
    dbms_output.put('Old salary: ' || :old.sal);
    dbms_output.put('  New salary: ' || :new.sal);
    dbms_output.put_line('  Difference ' || sal_diff);
END;

In this example the trigger fires BEFORE DELETE OR INSERT OR UPDATE :old.sal will contain the salary prior to the trigger firing and :new.sal will contain the new value.

PLSQL :NEW and :OLD, You normally use the terms in a trigger using :old to reference the old value and :​new to reference the new value. Here is an example from the  Best practices for managing old and new information and preventing FORALL errors By Steven Feuerstein . May/June 2007. I want to audit updates to a table, including the before and after values of each column in my table. To do this, I would love to pass :NEW and :OLD as arguments to procedures, but that doesn't seem to work.

:New and :Old Value can be differentiated in DML Statements . Insert -- :Old = NULL :New= Inserted new value

Update -- :Old = Value present in table before the Update statement Triggered :New = Given new value to Update

Delete -- :Old = Value before deletion :New = NULL

Using Triggers, About OLD and NEW Pseudorecords. When a row-level trigger fires, the PL/SQL runtime system creates and populates the two pseudorecords OLD and NEW . NEW and OLD are special variables that you can use with PL/SQL triggers without explicitly defining them. NEW is a pseudo-record name that refers to the new table row for insert and update operations in row-level triggers. Its usage is :NEW.column, where column is the name of a column in the table on which the trigger is defined.

NEW OLD « Trigger « Oracle PL/SQL Tutorial, NEW and OLD are special variables that you can use with PL/SQL triggers without explicitly defining them. NEW is a pseudo-  Old and new value : NEW OLD « Trigger « Oracle PL/SQL Tutorial. 10 11 / PL/SQL procedure successfully completed. SQL> SQL> drop table game_player; Table dropped

:new means the new value your are trying to insert :old means the existing value in database

Old and new value : NEW OLD « Trigger « Oracle PL/SQL Tutorial, Old and new value : NEW OLD « Trigger « Oracle PL/SQL Tutorial. NEW and OLD are pseudorecords that the PL/SQL runtime engine creates and populates whenever a row-level trigger fires. OLD and NEW store the original and new values, respectively, of the record being processed by the trigger. They are called pseudorecords because they do not have all properties of PL/SQL records.

:old is your old value :new is your new value,

it is used alot in triggers for example with Creation_Date & Modified_By fields

The Oracle PL/SQL NEW Keyword, Columns of the new pseudo record can be referenced by prefixing each column with :NEW identifier. Example Syntax: [:] [OLD | NEW] [.] [COLUMN NAME] You normally use the terms in a trigger using :old to reference the old value and :new to reference the new value. Here is an example from the Oracle documentation linked to above. CREATE OR REPLACE TRIGGER Print_salary_changes BEFORE DELETE OR INSERT OR UPDATE ON Emp_tab FOR EACH ROW WHEN (new.Empno > 0) DECLARE sal_diff number; BEGIN sal

Oracle Row-level Triggers, Home / PL/SQL Tutorial / Oracle Row-level Triggers ON table_name FOR EACH ROW REFERENCING OLD AS old_name NEW AS new_name WHEN  One part of the SQL CREATE TRIGGER syntax that you can use is the optional REFERENCING old_or_new_value_alias_list phrase. It enables you to create an alias or correlation name that references values in the trigger’s subject table. After you create a correlation name for new values or an alias for new table contents, you can then …

Oracle / PLSQL: AFTER UPDATE Trigger, The syntax to create an AFTER UPDATE Trigger in Oracle/PLSQL is: VALUES ( :new.order_id, :old.quantity, :new.quantity, v_username ); END; /. previous  CREATE OR REPLACE TRIGGER trg__log__salary__hike AFTER UPDATE OF SALARY ON employee__salary FOR EACH ROW WHEN ((NEW.SALARY - OLD.SALARY) > 50000) DECLARE username varchar2(20); BEGIN SELECT USER INTO username FROM dual; -- Insert new values into log table.

:Old and :New value in pl sql triggers, eTour.com is the newest place to search, delivering top results from across the web. Content updated daily for how to learn sql.

Comments
  • Are they just useful to display values after and before trigger is fired or is their any other usage?
  • @Pravin common use cases are validation and auditing. Using the above example imagine the requirement was to track an employees salary history, in this case we could insert the old salary, modification date and user name into a history table. In the application I'm working on ATM a trigger is used to update a records elevation when the coordinates are edited
  • And they are not just for reference too: in a before insert or update trigger a value could be assigned to the :new values. A common use is to provide a primary key with a value from a sequence in a before-insert trigger.
  • This behavior of OLD being null in insert and NEW being null in delete changes if the statement is using AFTER instead of BEFORE?
  • @Sawd No it does not. In BEFORE (insert or update) triggers you are allowed to modify the values, though, and the modifications will end up in the saved record.