Linux join utility complains about input file not being sorted

Question

I have two files:

file1 has the format:

field1;field2;field3;field4

(file1 is initially unsorted)

file2 has the format:

Answer 1

sort -k1 uses all fields starting from field 1 as the key. You need to specify a stop field.

sort -t\; -k1,1