How to use a package constant in SQL SELECT statement?

Question

How can I use a package variable in a simple SELECT query statement in Oracle?

Something like

SELECT * FROM MyTable WHERE TypeId = MyPackage.MY_TYPE
         


        

Answer 1

There is a more generic way which works fine for me. You create a function with input constant name (i.e. schema.package.constantname) and it returns you the constant value. You make use of executing immediate a PL/SQL block by binding res variable (see example).

Function looks like this:

CREATE OR REPLACE FUNCTION GETCONSTANTVALUE (i_constant IN VARCHAR2)  RETURN NUMBER deterministic AS

   res number; 
BEGIN

   execute immediate 'begin :res := '||i_constant||'; end;' using out res;     
   RETURN res;

END;
/

You can then use the constant of any package in any SQL, i.e. like

select GETCONSTANTVALUE('PKGGLOBALCONSTANTS.constantname') from dual;

Like this you need only 1 function and you take the advantage to use existing packages.constants.