How to I add a constant into a with block? - oracle

Question

In a with block, I can define function and query, I would like to define a constant too that I can reuse after.
the following code works.
WITH
FUNCTION a (a IN INTEGER)
RETURN INTEGER
IS
BEGIN
RETURN a + 1;
END;
b(v) AS (SELECT column_value FROM sys.ODCINUMBERLIST(1,2,3))
SELECT a (v) FROM b;
but this doesn't work.
WITH
c integer:=1;
FUNCTION a (a IN INTEGER)
RETURN INTEGER
IS
BEGIN
RETURN a + 1;
END;
b(v) AS (SELECT column_value FROM sys.ODCINUMBERLIST(1,2,3))
SELECT a (v) FROM b;
[Error] Execution (14: 20): ORA-00942: table or view does not exist
I know that I can create another query in the with block:
select 1 c from dual
But it doesn't look pretty if I have a lot of constants.
Is there a way to add constant in a with block?

Answer 1

Add another subquery factoring clause with exactly one row and define all the constants in there and then CROSS JOIN it to your other queries:
WITH FUNCTION a (a IN INTEGER)
RETURN INTEGER
IS
BEGIN
RETURN a + 1;
END;
constants (c1, c2, c3, c4) AS (
SELECT 1, 2, 3, 4 FROM DUAL
),
b(v) AS (
SELECT column_value FROM sys.ODCINUMBERLIST(1,2,3)
)
SELECT a(v), c.*
FROM b
CROSS JOIN constants c;
Or, you could declare a function for each constant:
WITH FUNCTION a (a IN INTEGER)
RETURN INTEGER
IS
BEGIN
RETURN a + 1;
END;
FUNCTION c1 RETURN INTEGER IS BEGIN RETURN 1; END;
FUNCTION c2 RETURN INTEGER IS BEGIN RETURN 2; END;
FUNCTION c3 RETURN INTEGER IS BEGIN RETURN 3; END;
FUNCTION c4 RETURN INTEGER IS BEGIN RETURN 4; END;
b(v) AS (
SELECT column_value FROM sys.ODCINUMBERLIST(1,2,3)
)
SELECT a(v), c1, c2, c3, c4
FROM b;
(However, using functions may introduce a performance overhead with repeated context-switches between SQL and PL/SQL scopes. Personally, I would use the first option.)
Which both output:
A(V)
C1
C2
C3
C4
2
1
2
3
4
3
1
2
3
4
4
1
2
3
4
db<>fiddle here