Example SOQL to query for all fields using Dyanamic Query in Apex

query-by-id

ID recordId = '5001a00000CgCE2';

DescribeSObjectResult describeResult = recordId.getSObjectType().getDescribe();

List<String> fieldNames = new List<String>( describeResult.fields.getMap().keySet() );

String query =
  ' SELECT ' +
      String.join( fieldNames, ',' ) +
  ' FROM ' +
      describeResult.getName() +
  ' WHERE ' +
      ' id = :recordId ' +
  ' LIMIT 1 '
;

// return generic list of sobjects or typecast to expected type
List<SObject> records = Database.query( query );

System.debug( records );