SOQL query giving error - illegal assignment from List to List

Question

trigger AccountCallableContact on Account (before insert) {
    for (Account acct : Trigger.new) {
        if (acct.Phone != Null) {
            LIST<Contact> MatchContact = [SELECT AccountId,
                                          COUNT(Id)
                                          FROM Contact
                                          WHERE Id = :acct.Id
                                          AND Phone != NULL
                                          GROUP BY AccountId];
        }
    }

}

Answer 1

The GROUP BY makes the SOQL an aggregate query and the result must be a List<AggregateResult>

See Apex doc on Aggregate queries

That said, your trigger is not bulkified as you are doing SOQL inside of a for loop. See Trailhead on how to avoid this