Using 'Between' operator after 'THEN' within 'CASE' statement within 'WHERE' Clause - sql

Question

Is it possible to use between operator within a CASE statement within a WHERE Clause ? For example in the code below, the condition should be pydate between (sysdate-12) and (sysdate-2) if its a monday and pydate between (sysdate-11) and (sysdate-1) if its a tuesday and so on. But the following doesn't work. May be there is another way of writing this. Can someone please help ?
select * from table_name
where pricekey = 'JUF' and
case when to_char(to_date(sysdate,'DD-MON-YY'), 'DY')='MON' then pydate between to_date(sysdate-12,'DD-MON-YY') and to_date(sysdate-2,'DD-MON-YY')
when to_char(to_date(sysdate,'DD-MON-YY'), 'DY')='TUE' then pydate between to_date(sysdate-11,'DD-MON-YY') and to_date(sysdate-1,'DD-MON-YY')
else pydate='sysdate'
end

Answer 1

You can apply the logic you are attempting, but it is done without the CASE. Instead, you need to create logical groupings of OR/AND to combine the BETWEEN with the other matching condition from your case.
This is because CASE is designed to return a value, rather than to dynamically construct the SQL inside it.
SELECT *
FROM table_name
WHERE
pricekey = 'JUF'
AND (
-- Condition 1
(to_char(to_date(sysdate,'DD-MON-YY'), 'DY') = 'MON' AND pydate BETWEEN to_date(sysdate-12,'DD-MON-YY') AND to_date(sysdate-2,'DD-MON-YY'))
-- Condition 2
OR (to_char(to_date(sysdate,'DD-MON-YY'), 'DY')='TUE' AND pydate BETWEEN to_date(sysdate-11,'DD-MON-YY') AND to_date(sysdate-1,'DD-MON-YY'))
-- ELSE case, matching neither of the previous 2
OR (to_char(to_date(sysdate,'DD-MON-YY'), 'DY') NOT IN ('MON', 'TUE') AND pydate = 'sysdate')
)

Answer 2

This is hard to write using a case. Just do:
where pricekey = 'JUF' and
((to_char(to_date(sysdate,'DD-MON-YY'), 'DY') = 'MON' and
pydate between to_date(sysdate-12,'DD-MON-YY') and to_date(sysdate-2,'DD-MON-YY')
) or
(to_char(to_date(sysdate,'DD-MON-YY'), 'DY') = 'TUE' and
pydate between to_date(sysdate-11,'DD-MON-YY') and to_date(sysdate-1,'DD-MON-YY')
) or
(o_char(to_date(sysdate,'DD-MON-YY'), 'DY') not in ('MON', 'TUE') and
pydate = trunc(sysdate)
)
)
Note, I also removed the single quotes around "sysdate", so it won't be treated as a string. And, I trunc'ed it to just get the date portion with no time.

Answer 3

First of all, sysdate is a date so don't use to_date on it.
Secondly, don't rely on day names. Once another language setting is chosen, your statement may not work anymore.
Then pydate is a date. sysdate is a date. Dont compare pydate to the string 'sysdate', but to sysdate.
It also seems that you are trying to remove the time part from sysdate with to_date(sysdate-11,'DD-MON-YY'). The function used for removing a time part of a datetime is trunc.
Then the case statement is supposed to return a value. There is no boolean data type in SQL, so you cannot evaluate an expression inside and return the result. Rather than doing so, you will return a valid data type such as a number or a string which you can compare outside:
select *
from table_name
where pricekey = 'JUF' and
case
when to_char(sysdate, 'DY', 'NLS_DATE_LANGUAGE=AMERICAN')='MON' then
case when pydate between trunc(sysdate)-12 and trunc(sysdate)-2 then 'GOOD' else 'BAD' end
when to_char(sysdate, 'DY', 'NLS_DATE_LANGUAGE=AMERICAN')='TUE' then
case when pydate between trunc(sysdate)-11 and trunc(sysdate)-1 then 'GOOD' else 'BAD' end
else
case when pydate = trunc(sysdate) then 'GOOD' else 'BAD' end
end = 'GOOD';
If pydate can have a time part, you may want to replace pydate with trunc(pydate), too.
Of course you can do all this with some ANDs and ORs and parentheses instead of CASE statements. It's up to you what is more readable for you.