create table #test(field1 int,field2 int,field3 varchar(50))
insert into #test select 1,5,'我'
insert into #test select 2,5,'我想'
insert into #test select 3,5,'我想你'
insert into #test select 3,5,'知道我想你吗'select top 1 * from #test where field1<=3 and field2>=3 order by len(field3) desc;drop table #test1.如上话句,实际只想取一条,请问加上top 1和不加上top 1 在效率上是否有区别?
2.根据实符的长度来排序,是否会大大降低效率?
insert into #test select 1,5,'我'
insert into #test select 2,5,'我想'
insert into #test select 3,5,'我想你'
insert into #test select 3,5,'知道我想你吗'select top 1 * from #test where field1<=3 and field2>=3 order by len(field3) desc;drop table #test1.如上话句,实际只想取一条,请问加上top 1和不加上top 1 在效率上是否有区别?
2.根据实符的长度来排序,是否会大大降低效率?
2.ORDER BY 会降低查询效率
2、效率会受到影响的,直接
select * from #test where field1<=3 and field2>=3 order by field3 desc;