在 NZSQL 中将 limit 与 union all 一起使用时出错

Question

我试图在一周的时间内随机抽样随机条目。为了确保平日和周末条目的平衡，我草拟了 2 个单独的 sql 语句，如下所示：

select * FROM admin.acct_activity
where RANDOM() <=1
        --weekday
        and extract(day from page_hit_ts) Between 6 and 10
limit 500
UNION all

SELECT *
FROM admin.acct_activity
where RANDOM() <=1
        --weekend
        and extract(day from page_hit_ts) Between 11 and 12
limit 200
/* to-do
 1. limit results for each query
 2. order query results by date*/

错误信息是：

"all" (at char 121) expecting a keyword (State:42000, Native Code: 1B)

这是在 Netezza SQL (NZSQL)

第一个 select 语句中的 limit 语句似乎导致了错误。有小费吗？

Answer 1

我认为你可以用括号来做到这一点：

(select *
 FROM admin.acct_activity
 where RANDOM() <=1 and extract(day from page_hit_ts) Between 6 and 10
 limit 500
)
UNION all
(SELECT *
 FROM admin.acct_activity
 where RANDOM() <=1 and extract(day from page_hit_ts) Between 11 and 12
 limit 200
)

如果没有，您绝对可以使用子查询来完成：

select t.*
from ((select *
       FROM admin.acct_activity
       where RANDOM() <=1 and extract(day from page_hit_ts) Between 6 and 10
       limit 500
      )
     UNION all
     (SELECT *
      FROM admin.acct_activity
      where RANDOM() <=1 and extract(day from page_hit_ts) Between 11 and 12
      limit 200
     )
    ) t