case when in where clause postresql - postgresql

Question

select service_code,service_cat_code,mobile_no,upper(applicant_name_eng) as name,to_char(license_date,'dd/mm/yyyy')as license_from,to_char(license_valid_upto,'dd/mm/yyyy')as license_to,Upper(license_no),district_code,taluk_code,CONCAT(address_building,', ', address_cityvillage,', ',address_locality,', ',address_landmark,', ',address_street) as address
from mst_license
WHERE cast(license_valid_upto as date) = case
WHEN license_valid_upto < now()
THEN
case
when license_valid_upto = '2021-06-30'
then 1 else 0
END
ELSE
case when license_valid_upto > now()
then 1 else 0
End
END
and Upper(license_no)='1SP146924BJP'
I want license valid should be either greater than now or if license valid less than now it must be with the date ''30/06/2021' but when i use above query i get error
ERROR: operator does not exist: date = integer
LINE 3: WHERE cast(license_valid_upto as date) = case
^
HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
SQL state: 42883
Character: 418
Help me out guys

Answer 1

The main issue you have is that your case statement returns an integer (1 or 0) but you are trying to compare that to a date, which you cannot do as Postgres is a strict data typing. Even if it did work it would always be false (well except for 1969-12-31/1970-01-01). Moreover the case structure is not needed. The best/correct to compare dates is just use date values. Since you did not indicate the data type for column license_valid_upto so based on how it is used I'll assume it is timestamp with timezone as that is what NOW() returns. Your query becomes:
select service_code
, service_cat_code
, mobile_no
, upper(applicant_name_eng) as name
, to_char(license_date,'dd/mm/yyyy')as license_from
, to_char(license_valid_upto,'dd/mm/yyyy')as license_to
, upper(license_no) as license_no
, district_code
, taluk_code
, concat(address_building,', '
,address_cityvillage,', '
,address_locality,', '
,address_landmark,', '
,address_street) as address
from mst_license
where and upper(license_no)='1SP146924BJP'
and ( cast(license_valid_upto as date) > cast( now() as date)
or (cast (icense_valid_upto as date) < cast( now() as date)
and cast (icense_valid_upto as date) = date '2021-06-30'
)
);
Also, learn for format your queries for readability and so you do not need to scroll right. You, and others looking at your queries later will appreciate it later.