linux - Join two csv files -

i need merge these 2 sorted csv files on 'contract' column (which common both files):

file1.csv

data;client;contract

mar 04 2017;la00024;1-456

mar 04 2017;la00025;1-789

file2.csv

contract;pda

1-456;00024

1-789;00025

the output i'd unique table:

data;client;contract;pda

mar 04 2017;la00024;1-456;00024

mar 04 2017;la00025;1-789;00025

however using command

$ join -o 1.1 1.2 1.3 2.2 -t";" -1 3 -2 1 file1.csv file2.csv

the result line

$ data;client;contract;pda

the join doesn't return merge of titles input files? why act this?

sort files before join.

join -o 1.1,1.2,1.3,2.2 -t ';' -1 3 -2 1 <(sort -n -t";" -k3 file1.csv) <(sort -n -t";" -k1 file2.csv) 

ps: sample data, command in question worked me. required , in -o format.