create table #tt(id int, dt datetime)
insert into #tt(id)
select 1 union all
select 2 union all
select 3
insert into #tt(id,dt)
select 4,'' union all
select 5,'' union all
select 6,''
select * from #tt
运行上面的,结果是
1 NULL
2 NULL
3 NULL
4 1900-01-01 00:00:00.000
5 1900-01-01 00:00:00.000
6 1900-01-01 00:00:00.000
也就是,你不指定值时,默认就是NULL,指定空值时,是1900-01-01.
SQL2000的是日期时间字段datetime