library(data.table)
dt1 <- data.table(mtcars)
dt1[c(cyl=='6',hp=='110'), qsec]

dt1[cyl=='6' || hp=='110', qsec]

[1] 16.46 17.02 18.61 19.44 17.02 20.22 15.84 20.00 22.90 18.30 18.90 17.40 17.60 18.00 17.98 17.82
[17] 17.42 19.47 18.52 19.90 20.01 16.87 17.30 15.41 17.05 18.90 16.70 16.90 14.50 15.50 14.60 18.60