sql 同一列的多行内容拼接成字符串

SELECT
L4.plan_id
,MAX(SUBSTR(L4.分组内容,2)) display_theme
FROM(
        SELECT
        L3.plan_id
        ,SYS_CONNECT_BY_PATH(L3.theme_name,'；') AS 分组内容
        FROM(
                SELECT
                L2.plan_id
                ,L2.theme_name
                ,L2.plan_id||L2.分组内编号 AS 分组字段加编号,L2.plan_id||(L2.分组内编号-1) AS 上级分组字段加编号
                FROM(
                        SELECT
                        L1.plan_id   -- 分组依据
                        ,L1.theme_name    -- 同一列中 要合并的不同行 的值
                        ,ROW_NUMBER() OVER (PARTITION BY L1.plan_id ORDER BY L1.theme_name ASC) 分组内编号
                        FROM t_display_config_theme L1
                ) L2
        ) L3
        START WITH L3.上级分组字段加编号 LIKE '%0'
        CONNECT BY PRIOR L3.分组字段加编号=L3.上级分组字段加编号
) L4
GROUP BY L4.plan_id