内连接vs where子句子查询sql server

Question

我正在尝试加快我的存储过程,所以我使用下面的统计信息以两种格式测试我的存储过程

方法1:使用join

set statistics io on 

select top 2000   
    p.Vehicleno, 
    dbo.GetVehicleStatusIcon1(p.Direction, StatusCode, 0) as 'Status',
    location,
    Convert(varchar(13), p.TrackTime, 102) + ' ' + Convert(varchar(13), p.TrackTime, 108) AS 'TrackTime',
    p.Speed, p.Ignition
from 
    pollingdata p 
inner join 
    assignvehicletouser asn on asn.vehicleno = p.vehicleno
where 
    asn.empid = 1

我得到统计结果为

Table 'Worktable'. Scan count 943, logical reads 7671, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'AssignVehicleToUser'. Scan count 1, logical reads 41, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'PollingData'. Scan count 1, logical reads 50, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

方法2:使用where子句子查询

set statistics io on 

select top 2000 
    Vehicleno,
    dbo.GetVehicleStatusIcon1(Direction,StatusCode, 0) as 'Status',
    location,
    Convert(varchar(13), TrackTime, 102) + ' ' + Convert(varchar(13), TrackTime, 108) AS 'TrackTime',
    Speed, Ignition
from 
    pollingdata 
where 
    vehicleno in (select vehicleno 
                  from assignvehicletouser 
                  where empid = 1)

我得到统计结果为

Table 'PollingData'. Scan count 1, logical reads 50, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'AssignVehicleToUser'. Scan count 1, logical reads 41, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

需要知道哪一个最好用？

需要解释逻辑读取如何在这里工作？

Answer 1

如果你不需要assignvehicletouser桌子上的任何东西,我宁愿EXISTS(它的工作方式可能相同IN)

SELECT TOP (2000) p.Vehicleno
    , dbo.GetVehicleStatusIcon1(p.Direction, StatusCode, 0) AS 'Status'
    , location
    , CONVERT(VARCHAR(13), p.TrackTime, 102) + ' ' + CONVERT(VARCHAR(13), p.TrackTime, 108) AS 'TrackTime'
    , p.Speed
    , p.Ignition
FROM pollingdata p
WHERE EXISTS (
        SELECT 1
        FROM assignvehicletouser asn
        WHERE asn.vehicleno = p.vehicleno
            AND asn.empid = 1
        );