PL/SQL: How do I declare session variables?

Question

How do I declare a session variable in PL/SQL - one that will persist for the duration of the session only, without me having to store it in the database itself?

Answer 1

You create a package level variable. This is a minimal example:

CREATE OR REPLACE PACKAGE my_package
AS
    FUNCTION get_a RETURN NUMBER;
END my_package;
/

CREATE OR REPLACE PACKAGE BODY my_package
AS
    a  NUMBER(20);

    FUNCTION get_a
    RETURN NUMBER
    IS
    BEGIN
      RETURN a;
    END get_a;
END my_package;
/

If you do this you should read up on (and handle correctly) ORA-04068 errors. Each database session will have it's own value for a. You can try this with:

SELECT my_package.get_a FROM DUAL;