创建表语句的一些疑问

[wwfxgm]

-- Create Employees table
CREATE TABLE dbo.Employees
(
  empid      INT                         NOT NULL
    CONSTRAINT PK_Employees PRIMARY KEY NONCLUSTERED,
  empname    VARCHAR(25)                 NOT NULL,
  department VARCHAR(50)                 NOT NULL,
  salary     NUMERIC(10, 2)              NOT NULL,
  sysstart   DATETIME2(0)
    GENERATED ALWAYS AS ROW START HIDDEN NOT NULL,
  sysend     DATETIME2(0)
    GENERATED ALWAYS AS ROW END   HIDDEN NOT NULL,
  PERIOD FOR SYSTEM_TIME (sysstart, sysend),
  INDEX ix_Employees CLUSTERED(empid, sysstart, sysend)
)
WITH ( SYSTEM_VERSIONING = ON ( HISTORY_TABLE = dbo.EmployeesHistory ) );
GO

第一个疑问：GENERATED ALWAYS AS ROW START HIDDEN NOT NULL，啥意思啊？
第二个疑问：WITH ( SYSTEM_VERSIONING = ON ( HISTORY_TABLE = dbo.EmployeesHistory ) 这个也不知道啥意思了。

[卖水果的net]

SQL Server 2016 的一个新特性，对原表进行改动后数据的历史记录表，这个特性 DB2 上也支持 你可以去官方看看，也可以先百度一下