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/**
 * Copyright (c) 2009-2016, Data Geekery GmbH (http://www.datageekery.com)
 * All rights reserved.
 *
 * Licensed 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.
 *
 * Other licenses:
 * -----------------------------------------------------------------------------
 * Commercial licenses for this work are available. These replace the above
 * ASL 2.0 and offer limited warranties, support, maintenance, and commercial
 * database integrations.
 *
 * For more information, please visit: http://www.jooq.org/licenses
 *
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 */
package org.jooq;

import static org.jooq.SQLDialect.CUBRID;
// ...
import static org.jooq.SQLDialect.H2;
import static org.jooq.SQLDialect.HSQLDB;
import static org.jooq.SQLDialect.MARIADB;
import static org.jooq.SQLDialect.MYSQL;
// ...
// ...
import static org.jooq.SQLDialect.POSTGRES;
// ...
// ...

import java.util.Collection;

/**
 * An ordered-set aggregate function.
 * 
 * An ordered-set aggregate function is an aggregate function with a mandatory
 * Oracle-specific WITHIN GROUP (ORDER BY ..) clause. An example is
 * LISTAGG: 
 * SELECT   LISTAGG(TITLE, ', ')
 *          WITHIN GROUP (ORDER BY TITLE)
 * FROM     T_BOOK
 * GROUP BY AUTHOR_ID
 *  The above function groups books by author and aggregates titles
 * into a concatenated string.
 * 
 * Ordered-set aggregate functions can be further converted into window functions
 * using the OVER(PARTITION BY ..) clause. For example: 
 * SELECT LISTAGG(TITLE, ', ')
 *        WITHIN GROUP (ORDER BY TITLE)
 *        OVER (PARTITION BY AUTHOR_ID)
 * FROM   T_BOOK
 * 
 *
 * @author Lukas Eder
 */
public interface OrderedAggregateFunction {

    /**
     * Add an WITHIN GROUP (ORDER BY ..) clause to the ordered
     * aggregate function
     */
    @Support({ CUBRID, H2, HSQLDB, MARIADB, MYSQL, POSTGRES })
    AggregateFilterStep withinGroupOrderBy(Field... fields);

    /**
     * Add an WITHIN GROUP (ORDER BY ..) clause to the ordered
     * aggregate function
     */
    @Support({ CUBRID, H2, HSQLDB, MARIADB, MYSQL, POSTGRES })
    AggregateFilterStep withinGroupOrderBy(SortField... fields);

    /**
     * Add an WITHIN GROUP (ORDER BY ..) clause to the ordered
     * aggregate function
     */
    @Support({ CUBRID, H2, HSQLDB, MARIADB, MYSQL, POSTGRES })
    AggregateFilterStep withinGroupOrderBy(Collection> fields);
}