@SuppressWarnings("unchecked")
    public SelfT external(Collection<ClickHouseExternalTable> tables) {
        checkSealed();

        externalTables.clear();
        if (tables != null) {
            for (ClickHouseExternalTable e : tables) {
                externalTables.add(ClickHouseChecker.nonNull(e, ClickHouseExternalTable.TYPE_NAME));
            }
        }

        return (SelfT) this;
    }
Sets external tables.

@param tables non-null external tables
@return the request itself
clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseRequest.java