public String toSQLString() {
    StringBuilder sqlBuilder = new StringBuilder();
    sqlBuilder.append("FROM").append(' ');
    for (int i = 0; i < prefixPaths.size(); i++) {
      sqlBuilder.append(prefixPaths.get(i).toString());
      if (i < prefixPaths.size() - 1) {
        sqlBuilder.append(", ");
      }
    }
    return sqlBuilder.toString();
  }
This class maintains information of {@code FROM} clause.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/statement/component/FromComponent.java