content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.sql.babel;
  
  /**
   * Enumerates the collection type of a table: {@code MULTISET} allows duplicates
   * and {@code SET} does not.
   *
   * <p>This feature is supported in Teradata, which originally required rows in a
   * table to be unique, and later added the {@code MULTISET} keyword to
   * its {@code CREATE TABLE} command to allow the duplicate rows.
   *
   * <p>In other databases and in the SQL standard, {@code MULTISET} is the only
   * supported option, so there is no explicit syntax.
   */
  public enum TableCollectionType {
    /**
     * Table collection type is not specified.
     *
     * <p>Defaults to {@code MULTISET} in ANSI mode,
     * and {@code SET} in Teradata mode.
     */
    UNSPECIFIED,
  
    /**
     * Duplicate rows are not permitted.
     */
    SET,
  
    /**
     * Duplicate rows are permitted, in compliance with the ANSI SQL:2011 standard.
     */
    MULTISET,
  }
  