Access中not in优化方式

Access中使用not in效率低下，可以使用外连接语句代替：

 

--改造前写法
SELECT TOP 50 StockholderID,HaveRate,HaveNum  
FROM (  
    SELECT StockholderID,HaveRate,HaveNum 
    FROM StockInfo 
    WHERE 
    CapitalStockID = 104
    AND StockholderID NOT IN ( 
    SELECT StockholderID FROM StockInfo WHERE 
    CapitalStockID = 105) 
    ORDER BY HaveRate DESC 
) AS A 



--改造后写法
SELECT TOP 50 StockholderID,HaveRate,HaveNum  
FROM (
SELECT a.StockholderID,a.HaveRate,a.HaveNum FROM StockInfo a left outer join ( 
SELECT c.StockholderID,c.HaveRate,c.HaveNum FROM StockInfo c WHERE c.CapitalStockID = 105
) as b 
on a.StockholderID = b.StockholderID 
WHERE CapitalStockID = 104 and b.StockholderID is null
ORDER BY a.HaveNum DESC
) as t 


--例子1
select TOP 50 a.Name,a.StockholderID,-5 from CollectNew a left outer join (
SELECT TOP 50 c.Name,c.StockholderID FROM CollectOld c ORDER BY OldNum DESC
) as b
on a.StockholderID=b.StockholderID 
where b.StockholderID is null 
ORDER BY a.NewNum DESC 
--排序后会按照a表获取结果，如果想要差异性内容，不能加排序，或者在外层嵌套一层查询Select * from（）ORDER ....


--例子二
select a.* from generator a left outer join (select c.busno,c.id from generator c,ta_generator d where c.busno=d.busno) as b
on a.busno=b.busno 
where b.busno is null