Nope wasn't me. let me just update it original date first_id second_id expenses  jul2020 400 0101 1000 jul2020 500 89 2001 aug2020 400 0202 1500 aug2020 500 89 2001 sep2020 402 0101 3200 sep2020 500 89 2001 oct2020 403 101 200 oct2020 500 89 2001 nov2020 400 202 100 nov2020 500 89 2001 the target table date first_id second_id expenses  jul2020 400 0101 1000 jul2020 500 89 2001 aug2020 400 0101 1500 aug2020 500 89 2001 sep2020 400 0101 3200 sep2020 400 89 2001 oct2020 400 0101 200 oct2020 500 89 2001 nov2020 400 0101 100 nov2020 500 89 2001 ... View more

YESSS and if the first ID is different than the original ( if it is, then the second ID will be the same as the original ID if you notice) change it to the original first ID ... View more

thank you for trying  lets say this is the original table date first_id second_id expenses  jul2020 400 0101 1000 jul2020 500 89 2001 aug2020 400 0202 1500 aug2020 500 89 2001 sep2020 402 0101 3200 sep2020 500 89 2001 oct2020 403 0101 200 oct2020 500 89 2001 nov2020 400 0202 100 nov2020 500 89 2001 If you notice customer 400 has second ID 0101. But during the years the first ID or the second ID changes (not both at the same time). I want the table to become something like that date first_id second_id expenses  jul2020 400 0101 1000 jul2020 500 89 2001 aug2020 400 0101 1500 aug2020 500 89 2001 sep2020 400 0101 3200 sep2020 400 89 2001 oct2020 400 0101 200 oct2020 500 89 2001 nov2020 400 0101 100 nov2020 500 89 2001 now the customer with first ID 400 and second 0101 keeps it's original values thought the year. After that I want to aggregate the expenses it by first ID ( I can do that) I just can't change the first ID or the second ID ... View more

no everything is numeric even ID. It's like this. As you can see we have different dates (but for the same date multiple customers). I notice that customer 258 for secondary ID 0004 during the years the ID or the secondary ID changes. And I wan to assign the same ID as the first date and the same secondary ID as the first date ( or any day just to be consistent). I want to to do this cause I want to know how many expenses each customer has during the years. There are like 50m obs.   date, ID, secondary ID, expenses jul2020 258 0004 1000 jul2020 xxx xxx xxx … …. …. ….. aug2020 258 0008 2000 aug2020 xxx xxx xxx aug2020 500 0004 1000   ... View more

yeah but if I do that and don't take into account that the ID for the same customer is changing for some months wouldn't I loose some sums?  ... View more

no everything is numeric even ID. It's like this. As you can see we have different dates (but for the same date multiple customers). I notice that customer 258 for secondary ID 0004 during the years the ID or the secondary ID changes. And I wan to assign the same ID as the frist date and the same secondary ID as the first date ( or any day just to be cnsistent). I want to to do this cause I want to know how many expenses each customer has during the years. There are like 50m obs.   date,      ID, secondary ID, expenses jul2020 258 0004 1000 jul2020 xxx xxxx xxx ...... .... .... ..... ...... .... .... ..... aug2020 258 0008 2000 aug2020 xxx xxxx xxx aug2020 500 0004 1000 ... View more

YESSS 🙂 ... correct thank you. And then I want to sum column d for each (unique) ID . Thank you PeterC ... View more