mlr --csv join -f emp-ids.csv -j name data.csv

The join verb merges two files on a key field, here name, combining columns from emp-ids.csv into the rows of data.csv. The -f flag names the file to join against and -j names the shared key column. Rows without a match are dropped unless -u is passed to keep unpaired records. This is Miller's answer to a SQL JOIN between two CSV tables.