Re: How to select unique records in PostgreSQL

Hi All,

I want to get the unique wallet_id from this table even it was repeated on multiple occasions I should calculate only once as well as if the wallet_id was calculated on previous month it shouldn't be calculate on next months

create table student_id

(

student_wallet_id int,

card_id int,

created_date date

)

insert into  student_id values ('w1', 'c1', '2022-04-01')

insert into  student_id values ('w1', 'c2', '2022-04-03')

insert into  student_id values ('w1', 'c3', '2022-04-04')

insert into  student_id values ('w1', 'c4', '2022-05-01')

insert into  student_id values ('w2', 'c1', '2022-05-01')

insert into  student_id values ('w2', 'c2', '2022-05-04')

insert into  student_id values ('w3', 'c4', '2022-05-05')

insert into  student_id values ('w3', 'c6', '2022-06-03)

insert into  student_id values ('w3', 'c7', '2022-06-05')

insert into  student_id values ('w3', 'c8', '2022-06-07')

expected output:

-------------------

months      count_wallet_id

2022-04      1

2022-05      2

2022-05      0

Regards

A.Rama Krishnan