log using levelsof,text replace
set obs 100000000
set rmsg on
gen r=runiform()
gen recno=_n
sort r
gen v=mod(recno,100000)
summarize
quietly levelsof v,local(wlevels)

gen x=mod(recno,100)
summarize
quietly levelsof x,local(xlevels)

gen y=mod(recno,10)
summarize
quietly levelsof y,local(ylevels)

drop v x y 

gen v=string(mod(recno,1000))
summarize
quietly levelsof v,local(vlevels)

gen x=string(mod(recno,100))
summarize
quietly levelsof x,local(xlevels)

gen y=string(mod(recno,10))
summarize
quietly levelsof y,local(ylevels)

quietly table y
collapse (sum) r,by(x)