How do I show a running total from the previous records?
I am guessing you have an sql server, but it should alspo work on other rdms that support window functions


SELECT 
Seller
, Amount
, SUM(Amount) OVER (PARTITION BY Seller ORDER BY Seller ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS RunningTotal 
FROM Sales
GO


Seller |  Amount | RunningTotal
:----- | ------: | -----------:
Alex   | 10.0000 |      10.0000
Alex   | 10.2500 |      20.2500
Alex   | 20.5500 |      40.8000
Jane   | 10.2500 |      10.2500
Pete   | 10.2500 |      10.2500
Sarah  | 15.0000 |      15.0000
Tracy  | 10.2500 |      10.2500
Tracy  | 11.0000 |      21.2500
Tracy  | 10.2500 |      31.5000


db&lt;&gt;fiddle here