Oracle function to return value from select with union - oracle

Question

I am trying to add this function to oracle db but it keeps throwing the following errors:
10/72 PLS-00049: bad bind variable 'COMMITID'
12/90 PLS-00049: bad bind variable 'COMMITID'
14/76 PLS-00049: bad bind variable 'COMMITID'
17/16 PL/SQL: ORA-00933: SQL command not properly ended
CREATE OR REPLACE FUNCTION GetLatestProfileChangeDateTime(commitId IN NUMBER)
RETURN DATE
AS
testing DATE;
BEGIN
select max(a) as dateOfChange
INTO testing
from
(
select max(created_date) a from image_set where reference_id = :commitId and created_date is not null
union
select max(date_of_change) a from preferred_agent_info_history where commit_id = :commitId and date_of_change is not null
union
select max(date_of_change) a from commit_history where commit_id = :commitId and date_of_change is not null
)
RETURN testing;
END;
The inner select statement works fine but when I try to implement it within a function, I can't get it to accept it. I've even tried removing the parameter binding in the select statements for a starting place but it will throw different errors.

Answer 1

You don't need bind variables in your function; you are using the function parameter in the SQL part of the function, so you can simply refer to it by its name.
For example:
SQL> create or replace function f1(p IN number) return number is
2 retVal number;
3 begin
4 select :p * 2 into retVal from dual;
5 return retVal;
6 end;
7 /
Warning: Function created with compilation errors.
SQL> sho err
Errors for FUNCTION F1:
LINE/COL ERROR
-------- -----------------------------------------------------------------
4/12 PLS-00049: bad bind variable 'P'
The right way:
SQL> create or replace function f1(p IN number) return number is
2 retVal number;
3 begin
4 select f1.p * 2 into retVal from dual;
5 return retVal;
6 end;
7 /
Function created.
SQL> select f1(3) from dual;
F1(3)
----------
6