I think this is simpler and doesn't need a subsub query. How many transactions per minute... ``` select Purchases, duration*1440, purchases/(duration*1440) as TxnPerMin from ( select event, count(event) as Purchases, julianday(max(`datetime`)) - julianday(min(`datetime`)) as duration from table1 where event ='end' ); ``` ``` Purchases,duration*1440,TxnPerMin 42767,1884.12331692874,22.6986204224219 ``` ``` 22.6986204224219*1884.12331692874 ```