SQL SERVER 如何声明一个变量

DECLARE @i AS INT;
SET @i = 10;
GO

或者

DECLARE @i AS INT = 10;
GO

表表达式形式

DECLARE @empname AS NVARCHAR(31);

SET @empname = (SELECT firstname + N' ' + lastname
                FROM HR.Employees
                WHERE mgrid = 2);

SELECT @empname AS empname;
GO