Question

我在下面的代码中定义了一个名为a.onhold_endtime的字段。我希望将该值作为整个SELECT语句的一部分返回，但是当我包含它时，别名a。*无法识别。它返回一个错误＆＃34; ERROR：缺少FROM-clause条目表＃34; a＆＃34; ＆＃34;

Select distinct 
woas.workorderid,
a.onhold_endtime,

(SELECT 
(SELECT count(*) AS work_hours
FROM   generate_series (b.onhold_starttime
                  , a.onhold_endtime - interval '1h'
                  , interval '1h') h
WHERE  EXTRACT(ISODOW FROM h) < 6
AND    h::time >= '08:00'
AND    h::time <= '18:00') 
FROM (
     SELECT DISTINCT woas.workorderid, 
        timestamp 'epoch' + 
        nth_value(wos.endtime,1)  OVER(PARTITION BY woas.workorderid ORDER BY wos.endtime ASC
                         ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
        /1000 * INTERVAL '1 second' as onhold_endtime from wo_status_info wos
    LEFT JOIN wo_assessment woas ON woas.assessmentid = wos.assessmentid
    WHERE tmp.workorderid = woas.workorderid AND wos.statusid = 1 AND wos.nextstatusid = 2
) as a
LEFT JOIN (
     SELECT DISTINCT woas.workorderid, 
        timestamp 'epoch' + 
        nth_value(wos.endtime,1)  OVER(PARTITION BY woas.workorderid ORDER BY wos.endtime ASC
                         ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
        /1000 * INTERVAL '1 second' as onhold_starttime from wo_status_info wos
    LEFT JOIN wo_assessment woas ON woas.assessmentid = wos.assessmentid
    WHERE 
        (wos.statusid = 2 AND wos.nextstatusid <> 2)
) as b ON a.workorderid = b.workorderid) AS onhold_difference1

FROM wo_assessment as tmp
LEFT JOIN wo_assessment woas ON tmp.assessmentid = woas.assessmentid
LEFT JOIN wo_status_info wos ON woas.assessmentid = wos.assessmentid
ORDER BY woas.workorderid ASC

有没有办法可以构建代码，这样我就可以使用＆＃34; a＆＃34;别名？

使用简化代码进行更新 我定义了一个名为＆＃34; onhold_endtime＆＃34;在子查询中，别名为＆＃34; a＆＃34;。我想在我的主SELECT语句中返回值a.onhold_endtime

Select distinct 
woas.workorderid,
a.onhold_endtime,

(SELECT 
        (SELECT count(*)) 
        FROM (
             SELECT DISTINCT woas.workorderid, 
                nth_value(wos.endtime,1)  OVER(PARTITION BY woas.workorderid ORDER BY wos.endtime ASC
                ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
            as onhold_endtime from wo_status_info wos
            WHERE y.workorderid = woas.workorderid AND wos.statusid = 1 AND wos.nextstatusid = 2
        ) as a
        LEFT JOIN (
             SELECT DISTINCT woas.workorderid, 
                nth_value(wos.endtime,1)  OVER(PARTITION BY woas.workorderid ORDER BY wos.endtime ASC
                ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
                as onhold_starttime from wo_status_info wos
            WHERE 
                (wos.statusid = 2 AND wos.nextstatusid <> 2)
        ) as b ON a.workorderid = b.workorderid) AS x

FROM wo_assessment as y
LEFT JOIN wo_assessment woas ON y.assessmentid = woas.assessmentid

Answer 1

简而言之 - 您可以在相关子查询中使用外部查询别名：

t=# select o.oid, (select o.datname||'*') from pg_database o limit 1;
  oid  | ?column?
-------+-----------
 13505 | postgres*
(1 row)

但不能做相反的事情：

t=# select b.*, (select o.datname||'*') b from pg_database o limit 1;
ERROR:  missing FROM-clause entry for table "b"
LINE 1: select b.*, (select o.datname||'*') b from pg_database o lim...

            ^

最接近预期的是：

t=# select oid,b.* from pg_database o, LATERAL (select o.datname||'*') b limit 1;
  oid  | ?column?
-------+-----------
 13505 | postgres*
(1 row)

从子查询中使用的别名中选择

1 个答案: