 	case greaterThanOrEqual
 	case and
 	case or
+	case add
+	case subtract
+	case multiply
+	case divide
 
 	func sql(dialect: SQLDialect) -> String {
 		switch self {

		case .greaterThanOrEqual: return ">="
		case .and: return "AND"
		case .or: return "OR"
		}
	}
}

	case type(SQLType)
	case columnDefinition(column: SQLColumn, type: SQLType, primary: Bool)
	case binaryOperator(SQLBinary)
	case unaryOperator(SQLUnary)
	case join(SQLJoin)
}

