Oracle数据库表起别名不用as，使用as报错

Oracle数据库给表起别名不要 as 关键字， 字段起别名用 as

实战sql 

-- 某个时间段统计该委托企业占比数量 ， 先分组查占比百分比，在机关名称左连接机关名称表，在查时间字段左连接表内多条记录时间内最新一条
SELECT
    a.*,
    b.createtime 
FROM
    (
    SELECT
        t.*,
        t1.swjgmc 
    FROM
        (
        SELECT
            STF_NSRSBH,
            STF_NSRMC,
            stf_djxh,
            stf_zgswskfj_dm,
            ROUND(
            SUM( CASE WHEN createtime BETWEEN to_date( '2022-01-01', 'yyyy-MM-dd' ) AND to_date( '2022-06-28', 'yyyy-MM-dd' ) + 1 THEN 1 ELSE 0 END ) / COUNT( * ),    2    ) * 100 || '%' sjzb,
    SUM( CASE WHEN createtime BETWEEN to_date( '2022-01-01', 'yyyy-MM-dd' ) AND to_date( '2022-06-28', 'yyyy-MM-dd' ) + 1 THEN 1 ELSE 0 END ) AS qjhs,
    COUNT( * ) AS zhs 
FROM
    TB_PLSB_WTSQGL 
WHERE
    yxbz = 'Y' 
    AND xqzt = '1' 
GROUP BY
    STF_NSRSBH,
    STF_NSRMC,
    stf_djxh,
    stf_zgswskfj_dm 
    ) t
    LEFT JOIN dm_gy_swjg t1 ON t.stf_zgswskfj_dm = t1.swjg_dm ) a
    LEFT JOIN (
    SELECT DISTINCT
        b.STF_NSRSBH,
        MAX( b.createtime ) AS createtime 
    FROM
        TB_PLSB_WTSQGL b 
    WHERE
        b.createtime BETWEEN to_date( '2022-01-01', 'yyyy-MM-dd' ) 
        AND to_date( '2022-06-28', 'yyyy-MM-dd' ) + 1 
    GROUP BY
        b.STF_NSRSBH 
    ) b ON a.STF_NSRSBH = b.STF_NSRSBH;