Apply aggregate functions to expressions

The following query shows how you can apply aggregate functions to arithmetic expressions, and declare display labels for their results:

Figure 1. Query

SELECT MAX (res_dtime - call_dtime) maximum,
   MIN (res_dtime - call_dtime) minimum,
   AVG (res_dtime - call_dtime) average
   FROM cust_calls;

The query finds and displays the maximum, minimum, and average amounts of time (in days, hours, and minutes) between the reception and resolution of a customer call, and labels the derived values appropriately. The query result shows these aggregate time-interval values that the query calculates:

Figure 2. Query result

maximum         minimum         average

5 20:55         0 00:01         1 02:56