001/**
002 * Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
003 * <p>
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 * <p>
008 * http://www.apache.org/licenses/LICENSE-2.0
009 * <p>
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package com.mybatisflex.core.query;
017
018import com.mybatisflex.core.dialect.IDialect;
019import com.mybatisflex.core.util.CollectionUtil;
020import com.mybatisflex.core.util.StringUtil;
021
022import java.util.List;
023
024public class DistinctQueryColumn extends QueryColumn {
025
026    private List<QueryColumn> queryColumns;
027
028    public DistinctQueryColumn(QueryColumn... queryColumns) {
029        this.queryColumns = CollectionUtil.newArrayList(queryColumns);
030    }
031
032    @Override
033    public String toSelectSql(List<QueryTable> queryTables, IDialect dialect) {
034        if (CollectionUtil.isEmpty(queryTables)) {
035            return "";
036        }
037        return " DISTINCT " + StringUtil.join(", ", queryColumns, queryColumn ->
038                queryColumn.toSelectSql(queryTables, dialect));
039    }
040}