SQL query to group by day

Question

I want to list all sales, and group the sum by day.

Sales (saleID INT, amount INT, created DATETIME)

NOTE: I am using SQL Server 2005.

Answer 1

For PostgreSQL:

GROUP BY to_char(timestampfield, 'yyyy-mm-dd')

or using cast:

GROUP BY timestampfield::date

if you want speed, use the second option and add an index:

CREATE INDEX tablename_timestampfield_date_idx ON  tablename(date(timestampfield));