SQL Server:创建表变量，主键约束定义中的错误

我正在尝试使用主键创建一个表变量.这两个语句有什么区别?为什么第一个不起作用?

I'm trying to create a table variable with primary key. What is the difference between these two statements? Why the first one does not work?

--This does not work
declare @tabvar table (
    rowid int identity(1, 1) not null,
    var1 int null,
        constraint PK_tabvar_rowid primary key clustered (rowid)
)

--This works
declare @tabvar1 table (
    rowid int identity(1, 1) not null primary key clustered,
    var1 int null
)