A compound-complex sentence contains at least two independent (main) clauses and at least one dependent (subordinate) clause:
I entered the parlour (independent), but no one seemed to notice me (independent) before I exclaimed some nonsense which I don't remember now (dependent).
The structure of compound complex sentences is greatly varied, that is why you should be very careful about the punctuation. Correct punctuation will help the reader to get your idea right.
Follow these simple steps when punctuating compound – complex sentences:
Define the main (independent) clauses and subordinate (dependent) clauses.
Punctuate the compound part of a sentence just as you would punctuate a stand- alone compound sentence.
Now do the same with the complex part of a sentence.