A simple SELECT
returns all relevant rows from the database. GROUP BY
applies aggregate functions, condensing SELECT
ed data into one summary row per grouping. What if mixing the two approaches is desired—what if data rows need to be combined with aggregate totals in the same result set?
T-SQL’s OVER
clause allows several kinds of functions to be applied to non-GROUP
ed BY
rows. Using OVER
, a simple SELECT
returning data rows can be expanded to include columns containing summary statistics. Traditionally, aggregate functions can only be used in conjunction with GROUP BY
or to produce a single row summary result set; when used with OVER
, these limitations are removed. Continue reading