SQL Query to find the previous row

Question

I want to update the transaction colum in the table that has previous transaction(TansactionSequence minus one) from Y to E.
Ex:Update Transaction colum 5 and 10 to E
Note: 1. TansactionSequence with 1 is always Y, and can have multiple Transaction Sequence numbers.
2. SequenceNo is a primary Key

Answer 1

It seems that you did not give all of details. Try this statement:

update T
set Transactions = 'E'
from 
(
    select *, lag(Transactions) over (partition by CreditCardNumber order by TransactionSequence) as pt 
    from MyTable
) T
where pt = 'E'