Either I don't understand your requirement or there's nothing easier than
| stats count(c1) as s1 count(c2) as s2 count(c3) as s3 by site
| eval t=s1+s2+s3
Either I don't understand your requirement or there's nothing easier than
| stats count(c1) as s1 count(c2) as s2 count(c3) as s3 by site
| eval t=s1+s2+s3