Question

The following query succeeds:

SELECT INTERVAL '00:00:00.000000' HOUR TO SECOND(6)
FROM DUAL;

The following fails:

SELECT INTERVAL time_field HOUR TO SECOND(6) -- time_field is a VARCHAR2(15)
FROM some_table;

w/ the following error:

ORA-00923: FROM keyword not found where expected

How do I fix my second query to pull back an HOUR TO SECOND INTERVAL?

When I try:

SELECT cast(time_field AS INTERVAL HOUR TO SECOND(6))
FROM some_table

I get the following:

ORA-00963: unsupported interval type

TEST SETUP:

CREATE TABLE some_table (
   time_field VARCHAR2(50)
);

INSERT ALL
INTO some_table (time_field) VALUES ('10:00:00.000000')
INTO some_table (time_field) VALUES ('12:00:00.000000')
INTO some_table (time_field) VALUES ('15:00:00.000000')
INTO some_table (time_field) VALUES ('17:00:00.000000')
INTO some_table (time_field) VALUES ('20:00:00.000000')
INTO some_table (time_field) VALUES (NULL)
SELECT * FROM DUAL;

Answer 1

You can use the TO_DSINTERVAL function; example here using a CTE to replicate your table:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT TO_DSINTERVAL('0 ' || time_field)
FROM some_table;

TO_DSINTERVAL('0'||TIME_FIELD)
---------------------------------------------------------------------------
+000000000 00:00:00.000000000

Note that to make the format something the function recognises, you have to supply a ‘days’ part, hence the prepending of the dummy '0 ' string.

Your fixed-value query returns a slightly different format (or at least displays slightly differently; interval daa types do not have format models in quite the same way as dates, so not sure how to express that accurately):

SELECT INTERVAL '00:00:00.000000' HOUR TO SECOND(6)
FROM DUAL;

INTERVAL'00:00:00.000000'HOURTOSECOND(6)
---------------------------------------------------------------------------
+00 00:00:00.000000

To replicate that you can cast this if you need to:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT CAST(TO_DSINTERVAL('0 ' || time_field) AS INTERVAL DAY TO SECOND(6))
FROM some_table;

CAST(TO_DSINTERVAL('0'||TIME_FIELD)ASINTERVALDAYTOSECOND(6))
---------------------------------------------------------------------------
+00 00:00:00.000000

… or just:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT CAST('0 ' || time_field AS INTERVAL DAY TO SECOND(6))
FROM some_table;

CAST('0'||TIME_FIELDASINTERVALDAYTOSECOND(6))
---------------------------------------------------------------------------
+00 00:00:00.000000

… which is pretty much what @catcall first suggested, but this also needs the '0 ' prepended, or you get an ORA-01867. (Or, if you try to use HOUR TO SECOND, ORA-00963, even with the prepended day value). However, I guess (and it is just a guess, though very slightly educated) that it’s doing an implicit TO_DSINTERVAL or similar, and I think I’d prefer to use an explicit one so I was sure what’s happening. That might just be me, though…

---

Using your sample data I too get an ORA-01867, but it’s caused by the null value. You can use a case to leave that as null in the result:

SELECT CASE WHEN time_field IS NULL THEN null
    ELSE CAST('0 ' || time_field AS INTERVAL DAY TO SECOND(6)) END
FROM some_table;

CASEWHENTIME_FIELDISNULLTHENNULLELSECAST('0'||TIME_FIELDASINTERVALDAYTOSECO
---------------------------------------------------------------------------
+00 10:00:00.000000
+00 12:00:00.000000
+00 15:00:00.000000
+00 17:00:00.000000
+00 20:00:00.000000


6 rows selected.