library(RMySQL)
library(tidyverse)
yhendus<-dbConnect(dbDriver("MySQL"), user='mart', password='ajutine1234', host=
'localhost', dbname='mart' )

paring<-dbSendQuery(yhendus, "SELECT first_name, last_name, 
  YEAR(date_of_birth) AS synniaasta, MIN(production_year), 
    MIN(production_year)-YEAR(date_of_birth) AS esmavanus
 FROM efis_film_maker
  JOIN efis_people ON efis_film_maker.people_id=efis_people.id
  JOIN efis_film ON efis_film_maker.film_id=efis_film.id 
  WHERE YEAR(date_of_birth) IS NOT NULL AND
    length(production_year)=4 AND
    efis_film_maker.classificator_code='FILM_MAKER_DIRECTOR'
  GROUP BY efis_people.id")
andmed=fetch(paring, n=-1)
noored=andmed %>% filter(synniaasta>=1985)
vanad=andmed %>% filter(synniaasta<=1955)
t.test(noored$esmavanus, vanad$esmavanus)