Is there an SQL query that will count the number of occurrences of an event WITHOUT grouping the data by the event being counted? - sql

Question

Note that I'm doing this in MS Access, so a solution using basic SQL operators would be appreciated.
Suppose you have a table where each row represents a coin flip in a series of coin flips.
Disclaimer: I'm using coin flips as an analogy so I don't have to explain my actual data set.
SELECT * FROM CoinFlips;
Id Flip Time
-------------------
1 Heads 1
2 Tails 2
3 Heads 3
4 Heads 4
5 Heads 5
6 Tails 6
How would you write a query that returns all of the rows above with an additional column that counts the number of 'head' flips that occurred up to that row's occurrence. In other words, this is what I want the result to look like:
Desired Output
Id Flip Time NumHeads
--------------------------------
1 Heads 1 1
2 Tails 2 1
3 Heads 3 2
4 Heads 4 3
5 Heads 5 4
6 Tails 6 4

Answer 1

To do this in MS Access, you need a correlated subquery or join/aggregation. Other databases have direct support for this functionality, but not MS Access.
select cf.*,
(select count(*)
from CoinFlips as cf2
where cf2.flip = 'Heads' and cf2.id <= cf.id
) as NumHeads
from CoinFlips as cf;

Answer 2

Well here is a solution
SELECT coinFlips.ID
,coinFlips.Flip
,coinFlips.TIME
,DCount("Flip", "coinFlips", "ID <=" & [Time] & "AND Flip ='Heads'") AS CountHeads
,DCount("Flip", "coinFlips", "ID <=" & [Time] & "AND Flip ='" & [Flip] & "'") AS CountEachOccurence
FROM coinFlips;