查询日期和之前的行

Question

我有下表：

create table MyTable (
    Id int Primary Key Identity,
    UserId int not null,
    StartUnixTime int not null,
    StopUnixTime int not null
)

我需要查询开始时间和结束时间之间的所有行，加上 StartUnixTime 最高的行（对于每个 UserId），该行小于多个 UserId 的给定开始日期。

目前我正在这样做：

select
    *
from MyTable
where UserId in (select Id from @users)
and (StartUnixTime between @start and @end)

union all

select
    *
from MyTable
where UserId in (select Id from @users)
and StartUnixTime < @start
and StartUnixTime in (
    select
        max(StartUnixTime)
    from MyTable as mt
    where mt.UserId in (select Id from @users)
    and mt.StartUnixTime < @start
    group by mt.UserId
)

是否有更高效的方法来执行此查询？也许没有工会？

Answer 1

加入@users 表变量并使用“row_number() where = 1”应该更快地选择每个 UserId 的顶部记录...

select
    t.Id,
    t.UserId,
    t.StartUnixTime,
    t.StopUnixTime
from MyTable t inner join @users u on t.UserId = u.Id
where t.StartUnixTime between @start and @end

union all

select
    Id,
    UserId,
    StartUnixTime,
    StopUnixTime
from (
    select
        t.*,
        topStart = row_number() over(partition by t.UserId order by t.StartUnixTime desc)
    from MyTable t inner join @users u on t.UserId = u.Id
    where t.StartUnixTime < @start
) tt
where
    topStart = 1