downloaded tsv files and lack of data inside

Hi all.
I downloaded IMDB tsv files
(name.basics.tsv.gz, title.basics.tsv.gz, title.episode.tsv.gz, title.ratings.tsv.gz,  title.akas.tsv.gz   title.crew.tsv.gz  and  title.principals.tsv)
but it seems there are lacks of datas here or there.
We can't find, for example, all datas related to a crew for a particular movie. A short list of them is given instead of a complete one.
Is it normal or have I misses something ?
Thank's for any suggestions