Creating a Time Dimension table with Intervals in Oracle - sql

Question

What is the easiest way to create a table in oracle to get the output as shown below;
Time Key
5 Minute Interval
10 Minute Interval
15 Minute Interval
100
12:00:00
12:10:00
12:15:00
101
12:05:00
12:10:00
12:15:00
102
12:10:00
12:20:00
12:15:00
103
12:15:00
12:20:00
12:30:00
The hours will be displayed in 24 hour format and will be used to join the time key onto a fact table to be loaded into a Microsoft Analysis Tabular Model.

Answer 1

Seems that you need a row generator. Here's an example.
Date format (just to know what you're looking at):
SQL> alter session set nls_date_format = 'dd.mm.yyyy hh24:mi:ss';
Session altered.
Query (creates 10 rows of data; change value in line #9 for more (or less) rows):
SQL> with temp (time_key, datum) as
2 (select 99, trunc(sysdate) datum from dual)
3 select
4 time_key + level time_key,
5 datum + ( 5 * (level - 1)) / (24 * 60) five_min,
6 datum + (10 * (level - 1)) / (24 * 60) ten_min,
7 datum + (15 * (level - 1)) / (24 * 60) fifteen_min
8 from temp
9 connect by level <= 10;
TIME_KEY FIVE_MIN TEN_MIN FIFTEEN_MIN
---------- ------------------- ------------------- -------------------
100 04.01.2021 00:00:00 04.01.2021 00:00:00 04.01.2021 00:00:00
101 04.01.2021 00:05:00 04.01.2021 00:10:00 04.01.2021 00:15:00
102 04.01.2021 00:10:00 04.01.2021 00:20:00 04.01.2021 00:30:00
103 04.01.2021 00:15:00 04.01.2021 00:30:00 04.01.2021 00:45:00
104 04.01.2021 00:20:00 04.01.2021 00:40:00 04.01.2021 01:00:00
105 04.01.2021 00:25:00 04.01.2021 00:50:00 04.01.2021 01:15:00
106 04.01.2021 00:30:00 04.01.2021 01:00:00 04.01.2021 01:30:00
107 04.01.2021 00:35:00 04.01.2021 01:10:00 04.01.2021 01:45:00
108 04.01.2021 00:40:00 04.01.2021 01:20:00 04.01.2021 02:00:00
109 04.01.2021 00:45:00 04.01.2021 01:30:00 04.01.2021 02:15:00
10 rows selected.
SQL>
In Oracle, there's no "time" datatype. We use date and it consists of both date AND time. Your example shows that you want time only; well, you can't have it, not as a date datatype. You can use e.g. TO_CHAR function on it (and fetch only time component). I wouldn't recommend you to store those values as strings into varchar2 datatype column as nothing prevents you (or someone else) to put e.g. 12:3f:75 into it, and that certainly isn't valid time value.
So, you'd then:
SQL> create table test as
2 with temp (time_key, datum) as
3 (select 99, trunc(sysdate) datum from dual)
4 select
5 time_key + level time_key,
6 datum + ( 5 * (level - 1)) / (24 * 60) five_min,
7 datum + (10 * (level - 1)) / (24 * 60) ten_min,
8 datum + (15 * (level - 1)) / (24 * 60) fifteen_min
9 from temp
10 connect by level <= 10;
Table created.
SQL> select time_key,
2 to_char(five_min, 'hh24:mi:ss') five_min
3 from test;
TIME_KEY FIVE_MIN
---------- --------
100 00:00:00
101 00:05:00
102 00:10:00
103 00:15:00
104 00:20:00
105 00:25:00
106 00:30:00
107 00:35:00
108 00:40:00
109 00:45:00
10 rows selected.
SQL>
To answer question T. Peter posted as a comment: I don't know for other databases, but - principle that should work elsewhere is to use a cross join (Cartesian product) with a subquery that returns "a lot of rows". In Oracle, ALL_OBJECTS is such a table. It isn't indefinite; in my sample schema, it contains ~8000 rows. For example (see lines #8 - 10):
SQL> with temp (time_key, datum) as
2 (select 99, trunc(sysdate) datum from dual)
3 select
4 time_key + rn time_key,
5 datum + ( 5 * (rn - 1)) / (24 * 60) five_min,
6 datum + (10 * (rn - 1)) / (24 * 60) ten_min,
7 datum + (15 * (rn - 1)) / (24 * 60) fifteen_min
8 from temp cross join (select rownum rn
9 from all_tables
10 where rownum <= 10
11 );
TIME_KEY FIVE_MIN TEN_MIN FIFTEEN_MIN
---------- ------------------- ------------------- -------------------
100 04.01.2021 00:00:00 04.01.2021 00:00:00 04.01.2021 00:00:00
101 04.01.2021 00:05:00 04.01.2021 00:10:00 04.01.2021 00:15:00
<snip>
Basically, keyword here is "row generator". I suggest you Google for it and add database name you use.

Answer 2

You can use a recursive sub-query factoring clause and get the time values using INTERVAL DAY TO SECOND data type:
CREATE TABLE table_name ( time_key, five_minute, ten_minute, fifteen_minute ) AS
WITH data ( time_key, five_minute, ten_minute, fifteen_minute, num_rows ) AS (
SELECT 100,
INTERVAL '12:00' HOUR TO MINUTE,
INTERVAL '12:00' HOUR TO MINUTE,
INTERVAL '12:00' HOUR TO MINUTE,
4
FROM DUAL
UNION ALL
SELECT time_key + 1,
five_minute + INTERVAL '5' MINUTE,
ten_minute + INTERVAL '10' MINUTE,
fifteen_minute + INTERVAL '15' MINUTE,
num_rows - 1
FROM data
WHERE num_rows > 1
)
SELECT time_key,
five_minute,
ten_minute,
fifteen_minute
FROM data;
Then the table contains:
TIME_KEY | FIVE_MINUTE | TEN_MINUTE | FIFTEEN_MINUTE
-------: | :---------------------------- | :---------------------------- | :----------------------------
100 | +000000000 12:00:00.000000000 | +000000000 12:00:00.000000000 | +000000000 12:00:00.000000000
101 | +000000000 12:05:00.000000000 | +000000000 12:10:00.000000000 | +000000000 12:15:00.000000000
102 | +000000000 12:10:00.000000000 | +000000000 12:20:00.000000000 | +000000000 12:30:00.000000000
103 | +000000000 12:15:00.000000000 | +000000000 12:30:00.000000000 | +000000000 12:45:00.000000000
db<>fiddle here