Question

我试图随机抽样一个星期的随机条目。为了确保我有平日和周末条目的余额，我已经勾勒出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）

中

第一个select语句中的limit语句似乎会导致错误。有什么提示吗？

Answer 1

我认为你可以用括号做到这一点：

(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，你肯定可以用子查询来做到这一点：

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

Answer 2

每个查询只能设置一个LIMIT语句。您应该将每个有限查询放入临时表，然后UNION ALL临时表。

在NZSQL中使用与union all的限制时出错

2 个答案: