Sum case from previous month

Question

I couldn't find the answer to this on here or on google.

This is part of the main table

+---+-------+----------------+--------------+
|   |  Acct | Last_trans_date|Last_transpay |
+---+-------+----------------+--------------+
| 1 | ABC   | July 31        | Nov 5        |
| 2 | DEF   | Mar 1          | Aug 8        |
| 3 | GFH   | Mar 9          | Feb 7        |
+---+------+-----------------+--------------+

I want the total account for the previous month that includes last_trans_date and Last_transpay = previous month as count.

I used this

Select
year(open)
sum(case when month(last_trans_date) = month(current date - 1) and month(last_transpay) = month(current_date - 1) then 1 else 0 end) as activity
from table
group by 1.

I don't think it's outputting the correct amount

Answer 1

SELECT Count(*) 
FROM [table]
WHERE 
    CHARINDEX(@PrevMonth, Last_trans_date) = 1
    AND CHARINDEX(@PrevMonth, Last_transpay) = 1