Re: why I can't group by an expression

I believe using "GROUP BY region, date" will group by month(date) using the alias "date" > I want to create a summary table aggregating the sales based on the > month and region. But in my base table, there is only a date field, > I have to use month(date) to get the month, but I can't use > "group by region, month(date)" to create the summary table. > > My SQL looks like: > > insert into sum_mon_reg > select region, > sum(sales) sum_sales, > month(date) date > from sales > group by region, month(date)>