Is there a way to use SYSDATE with a weekly date? - sql

Question

So I've been trying to fetch some daily data with SYSDATE on a date type YYYYMMDD as following:
SELECT dates, trunc(calendar_date, 'DD') calendar_dates, weekday_nbr
FROM db.date
WHERE dates BETWEEN to_char(TRUNC(SYSDATE)-2, 'YYYYMMDD') AND to_char(TRUNC(SYSDATE)-1, 'YYYYMMDD')
But now I'm trying to use the same but on a YYYY+MM+Week date type with not much success
I tried using:
SELECT T time, period, fiscal_week
FROM db.time
WHERE time BETWEEN to_char(TRUNC(SYSDATE)-2, 'W') AND to_char(TRUNC(SYSDATE)-1,'W')
With time as a 7 digit number, and period and fiscal week as a 2 digit number
Knowing that there's no way I can truncate such date type, how can TRUNC SYSDATE YYYY+MM+Week to get the data on the last 2 weeks?
Also I was thinking about maybe getting the totals from a set day and then dropping all but the last 2 weeks, but on the long run maybe that would be time consuming.

Answer 1

Knowing that there's no way I can truncate such date type, how can TRUNC SYSDATE YYYY+MM+Week to get the data on the last 2 weeks?
Assuming that your fiscal weeks are from Monday-Sunday then you can truncate to the start of the ISO week (which is always Midnight on Monday) and use that for the basis of the comparison:
SELECT *
FROM db.time
WHERE dates >= TRUNC(SYSDATE, 'IW') - INTERVAL '14' DAY
AND dates < TRUNC(SYSDATE, 'IW')
If you have a column that is for weeks then you should still use a DATE data type and add a CHECK constraint (and can use virtual columns to generate the week and the year):
CREATE TABLE time (
dt DATE
CHECK (dt = TRUNC(dt, 'IW')),
year NUMBER(4,0)
GENERATED ALWAYS AS (EXTRACT(YEAR FROM dt)),
month NUMBER(2,0)
GENERATED ALWAYS AS (EXTRACT(MONTH FROM dt)),
week NUMBER(1,0)
GENERATED ALWAYS AS (FLOOR((dt - TRUNC(dt, 'MM'))/7) + 1),
time VARCHAR2(7)
GENERATED ALWAYS AS (
CAST(
TO_CHAR(dt, 'YYYYMM')
|| (FLOOR((dt - TRUNC(dt, 'MM'))/7) + 1)
AS VARCHAR2(7)
)
)
-- ...
);
fiddle
Then you can use the logic above on the date column.
If you do not have a DATE column then you will need to convert your YYYYMMW number into a DATE and then use the logic above.
For example, if the logic for your fiscal weeks (which you have not described) is that the first week of each month starts on the first Monday of the month then you can convert the YYYYMMW number to a DATE using:
SELECT NEXT_DAY(
TO_DATE(SUBSTR(time, 1, 6), 'YYYYMM') - INTERVAL '1' DAY,
'MONDAY'
) + INTERVAL '7' DAY * (SUBSTR(time, 7, 1) - 1) AS week_start
FROM db.time
and then could use it to filter the table using:
SELECT *
FROM (
SELECT t.*,
NEXT_DAY(
TO_DATE(SUBSTR(time, 1, 6), 'YYYYMM') - INTERVAL '1' DAY,
'MONDAY'
) + INTERVAL '7' DAY * (SUBSTR(time, 7, 1) - 1) AS week_start
FROM db.time t
)
WHERE week_start >= TRUNC(SYSDATE, 'IW') - INTERVAL '14' DAY
AND week_start < TRUNC(SYSDATE, 'IW')
If you have different logic for calculating when fiscal weeks start then you will need to apply that logic to the conversion.