我有以下postgres数据库的SQL语句：select roadcode,roadname,roadstart,roadends,f044 from gpsxd WHERE roadcode in ('X020360902') ORDER BY roadcode,roadstart ，此语句查询出的结果是每条路线的最小分段，如下数据 roadcode roadname roadstart roadends f044 X020360902 湾里-沙江 0 2.987 11101360902 X020360902 湾里-沙江 2.987 3.42 11101360902 X020360902 湾里-沙江 3.42 5.109 11101360902 X020360902 湾里-沙江 5.109 8.157 11101360902 X020360902 湾里-沙江 8.157 8.326 11101360521 X020360902 湾里-沙江 8.326 8.926 11101360902 ，现需求对结果进行分组，重组的要求是将按roadcode和f044分组，其中分组结果里的roadends和roadstart 相同时视为连续的路段，比如分组后的路线编码X020360902 结果数据应该是如下 roadcode roadname roadstart roadends f044 X020360902 湾里-沙江 0 8.157 11101360902 X020360902 湾里-沙江 8.157 8.326 11101360521 X020360902 湾里-沙江 8.326 8.926 11101360902 最终生成一个函数

以下是一个 PostgreSQL 函数，可以实现你所需的结果：

CREATE OR REPLACE FUNCTION group_road_segments()
RETURNS TABLE (roadcode text, roadname text, roadstart numeric, roadends numeric, f044 text) AS
$$
DECLARE
    result record;
    last_roadcode text := '';
    last_f044 text := '';
    last_roadstart numeric := 0;
    last_roadends numeric := 0;
BEGIN
    FOR result IN SELECT roadcode, roadname, roadstart, roadends, f044 FROM gpsxd WHERE roadcode IN ('X020360902') ORDER BY roadcode, roadstart LOOP
        IF result.roadcode <> last_roadcode OR result.f044 <> last_f044 OR result.roadstart <> last_roadends THEN
            IF last_roadcode <> '' THEN
                RETURN NEXT (last_roadcode, result.roadname, last_roadstart, last_roadends, last_f044);
            END IF;
            last_roadcode := result.roadcode;
            last_f044 := result.f044;
            last_roadstart := result.roadstart;
        END IF;
        last_roadends := result.roadends;
    END LOOP;
    IF last_roadcode <> '' THEN
        RETURN NEXT (last_roadcode, result.roadname, last_roadstart, last_roadends, last_f044);
    END IF;
END;
$$ LANGUAGE plpgsql;

该函数返回一个表，其中包含按 roadcode 和 f044 分组的结果，其中相邻的路段将被组合成单个路段。你可以将 'X020360902' 替换为其他 roadcode 值以查询不同的数据。请注意，该函数假定数据已按 roadcode 和 roadstart 排序。