http://salesforce.stackexchange.com/questions/133810

updateContatoPonto.trigger

trigger updateContatoPonto on Ponto__c (before insert, before update) {

	Map<Integer, Id> contactsByNumber = new Map<Integer, Id>();
	for(Ponto__c record: Trigger.new) {
		if(record.Inscricao_Number__c != null) {
			contactsByNumber.put(record.Inscricao_Numero__c.intValue(), null);
		}
	}
	// Ignore null
	contactsByNumber.remove(null);
	for(Contact record: [SELECT Inscricao_Numero__c FROM Contact WHERE Inscricao_Numero__c IN :contactsByNumber.keySet()]) {
		contactsByNumber.put(record.Inscricao_Numero__c.intValue(), record.Id);
	}
	for(Ponto__c record: Trigger.new) {
		record.Contato__c = contactsByNumber.get(record.Inscricao_Numero__c);
	}
}