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select b.id,b.title,b.smallclassid,s.shiname,q.quname,sc.smallclassname
from buy b inner join shi s on s.id=b.shi
inner join qu q on q.id=b.qu
inner join smallclass sc on sc.id=b.smallclassid
where b.smallclassid=68 and b.shi=1 and b.IsCheck=1
select b.id,b.title,b.smallclassid,s.shiname,q.quname,sc.smallclassname
from buy b inner join shi s on s.id=b.shi
inner join qu q on q.is=b.qu
inner join smallclass sc on sc.id=b.smallclassid
where b.smallclassid=68 and b.shi=1 and b.IsCheck=1
SQL codeSQL codeSELECT Buy.ID,Buy.Title,Buy.SmallClassID,
shi.shiName,qu.quName,SmallClass.SmallClassName
FROM Buy,Shi,Qu, SmallClass
WHERE Buy.SmallClassID=68 and Buy.shi=1 and Buy.IsCheck=1
and Buy.shi=shi.ID AND Buy.qu=qu.ID AND Buy.SmallClassID=SmallClass.ID
2、建一个组合索引create index IX_Buys on buy(SmallClass,shi,IsCheck),但是必须 注意这三个字段在Buy表的重复率,重复率低的排在前面 SELECT Buy.ID,Buy.Title,Buy.SmallClassID,shi.shiName,qu.quName,SmallClass.SmallClassName
FROM Buy join shi on Buy.shi=shi.ID join qu on Buy.qu=qu.ID
join SmallClass on Buy.SmallClassID=SmallClass.ID
where buy.SmallClassID=68 and buy.shi=1 and buy.IsCheck=1