Re: How to select unique records in PostgreSQL

Ron <ronljohnsonjr@xxxxxxxxx> · Fri, 25 Nov 2022 08:50:08 -0600



    Honestly, you do it in PostgreSQL the same way you do it in
    all the other SQL RDBMSs.

    
    On 11/24/22 06:01, Rama Krishnan wrote:

    
                                    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

                                    
    -- 

      Angular momentum makes the world go 'round.