[am]king ~/a/tm$ cat first.csv 
apple,5
pear,4
ananas,6
watermelon,10
salad,5
carrot,6
peach,5
apricot,7
[am]king ~/a/tm$ cat second.csv 
peach,orange
watermelon,green
ananas,yellow,expensive
apple,red
banana,yellow
apple,red
pea,brown
apricot,orange
pear,yellow
spinach,green
salad,green

##</code><code>##

[am]king ~/a/tm$ sort first.csv > first.s
[am]king ~/a/tm$ sort second.csv > second.s
[am]king ~/a/tm$ join -v1 -t, first.s second.s
carrot,6
[am]king ~/a/tm$ join -v2 -t, first.s second.s
banana,yellow
pea,brown
spinach,green