I am doing SQL Server query calculations and the division always gives me zero.
SUM(sl.LINES_ORDERED) , SUM(sl.LINES_CONFIRMED) , SUM(sl.LINES_CONFIRMED) /
It will be because you're divinding two integers.
Convert the two values in the division to decimals first:
, SUM(convert(decimal(12,2),sl.LINES_CONFIRMED)) / SUM(convert(decimal(12,2),sl.LINES_ORDERED)) AS 'Percent'