what is query for this one?

Question

I have a table with 3 columns id, homeph, mobileph.

If homeph is equal to mobileph, then homeph or mobileph with other line what is query for this?

Answer 1

In Oracle, you could use:

SELECT DISTINCT id, phone
FROM   input_table
UNPIVOT (
  phone FOR type IN (homeph, contactph) 
)

But it will be more efficient to check if the phone numbers are identical before unpivoting (as UNPIVOT will, by default, ignore NULL values):

SELECT id, phone
FROM   (
  SELECT id,
         homeph,
         CASE WHEN homeph = contactph THEN NULL ELSE contactph END AS contactph
  FROM   input_table
)
UNPIVOT (
  phone FOR type IN (homeph, contactph) 
)

Which, for the sample data:

CREATE TABLE input_table (id, homeph, contactph ) AS
  SELECT 1, 99999, 88888 FROM DUAL UNION ALL
  SELECT 2, 77777, 77777 FROM DUAL;

Both output:

ID	PHONE
1	99999
1	88888
2	77777

fiddle