SQLite |从两个（模式）相同的表中检索数据

Question

我有一个SQLite Database，我用以下query从两个表中获取数据。

select ie.* 
from (select * 
      from History where Station = @station and TimeStampCome <= @till and TimeStampCome >= @from 
      union all 
      select * 
      from Pending where Station = @station and TimeStampCome <= @till and TimeStampCome >= @from
     ) ie 
order by TimeStampCome desc LIMIT 100 OFFSET 1

这是最好和最有效的方式吗？我在alarm objects存储了database。因此，可以容易地超过1百万个条目。

Answer 1

对于您的特定查询，最好先限制每个表中的行，如下所示：

with h as (
      select h.*
      from history h
      where Station = @station and TimeStampCome <= @till and TimeStampCome >= @from 
      order by TimeStampCome desc
      limit 101
     ),
     p as (
      select p.*
      from pending p
      where Station = @station and TimeStampCome <= @till and TimeStampCome >= @from 
      order by TimeStampCome desc
      limit 101
     )
select pe.*
from (select h.* from h union all
      select p.* from p
     ) pe
order by TimeStampCome desc
limit 100 offset 1;

但是，如果您开始使用不同的偏移量，这将变得不太可行。

请注意，如果需要考虑性能，请从两个表中的(Station, TimeStampCome)上的索引开始。