将列声明为主键并向表中添加数据时为空统计信息

如果我将表中的列声明为主键,则会为该列创建统计信息,但即使向表中添加了大量数据,这些统计信息也是空的。如果我在添加数据后将主键添加到able,那么stats将填充有意义的信息。为什么预先创建主键不会产生有意义的统计信息,不管我向表中添加了多少数据?

案例1 :下面是使用主键创建表的代码:

create table t
(
    col1  int primary key,
    col2 int 
)
go

--insert 150000 records into table
insert into t (col1, col2)
    select top 150000 
        row_number() over (order by (select null)), 
        row_number() over (order by (select null)) 
    from 
        master.dbo.syscolumns 
    cross join 
        master.dbo.syscolumns as c

案例2 :下面是创建表的代码,其中的主键是在将数据摄取到表中之后创建的:

create table t
(
    col1 int not null,
    col2 int 
)
go

--insert 150000 records into table
insert into t (col1, col2)
    select top 150000 
        row_number() over (order by (select null)), 
        row_number() over (order by (select null)) 
    from 
        master.dbo.syscolumns 
    cross join 
        master.dbo.syscolumns as c

alter table t 
add constraint pk_col1 primary key (col1)

对于案例1,即使我试图通过对col1进行过滤来搜索索引,即使这样,统计信息也不会更新:

select * 
from t 
where col1 = 4050

对列进行筛选通常会创建统计信息,即使表是堆:

create table t1
(
    col1  int,
    col2 int 
)
go

--insert 15000 records into table
insert into t (col1, col2)
    select top 150000 
        row_number() over (order by (select null)), 
        row_number() over (order by (select null)) 
    from 
        master.dbo.syscolumns 
    cross join 
        master.dbo.syscolumns as c

select * 
from t1 
where col1 = 4050