Custom SQL fields - Command to calculate duration in days between two dates

What to use in Custom SQL field:

DATEDIFF(DD,[Table: Field Date1],[Table: Field Date2])

Example:

where

[Table: Field Date1] = [Assignment: Start Date]

[Table: Field Date2] = [Assignment: Actual End Date]

To calculate the weekday date difference between two dates in the system

DATEDIFF(dd,[Assignment: Create Date],[Assignment: Last Update Date]) - (2 * DATEDIFF(wk,[Assignment: Create Date],[Assignment: Last Update Date]))