List<Case> casesForCC = [
		SELECT Work_Order__r.IOL_QuoteId__r.IOLF_NumeroCommissione__c
		FROM Case
		WHERE IOLE_Processo_di_Lavorazione__c != NULL AND Work_Order__c != NULL AND Work_Order__r.IOL_QuoteId__r.Owner.LastName = 'Piscozzi'
];

Set<String> numeriCommissione = new Set<String>();
for(Case c : casesForCC) {
	if(String.isNotBlank(c.Work_Order__r.IOL_QuoteId__r.IOLF_NumeroCommissione__c)) {
		numeriCommissione.add(c.Work_Order__r.IOL_QuoteId__r.IOLF_NumeroCommissione__c);
	}
}

List<Case> cases = [
		SELECT Work_Order__r.IOL_QuoteId__r.IOLF_NumeroCommissione__c
		FROM Case
		WHERE IOLE_Processo_di_Lavorazione__c != NULL AND Work_Order__c != NULL AND Work_Order__r.IOL_QuoteId__r.IOLF_NumeroCommissione__c IN :numeriCommissione
];

List<String> caseIds = new List<String>();
for(Case c : cases) {
	caseIds.add(c.Id);
}

System.debug(caseIds.size());