如何复制时间戳数据类型

Question

我有一张带有TIMESTAMP 列的表格：

create  table dbo.EX_EMPLOYEE (
    NAME_X            varchar(10) null,
    RECORD_TIME_STAMP timestamp   null
    )

当我将行从一个表复制到另一个表时，使用：

SELECT * INTO EX_EMPLOYEE_T 
    FROM EX_EMPLOYEE 
    WHERE 1=0

或：

INSERT INTO EX_EMPLOYEE_T
    SELECT * 
        FROM EX_EMPLOYEE

我收到此警告：

警告：用户不能将非空值插入TIMESTAMP 列。数据库时间戳值已被插入到 TIMESTAMP 字段中。

目标表中的TIMESTAMP 列替换为当前数据库时间戳。

我的问题
如何复制带有TIMESTAMP 列的行，同时保留源表中的TIMESTAMP 值？

(有没有类似SET IDENTITY ON/OFF的设置)

我的场景
我有 2 个表，一个用于“实时”数据，另一个用于“备份”，所以我需要复制带有 TIMESTAMP 完整的行。我需要它完好无损，以便检测“实时”行是否发生了变化。

Answer 1

Sybase（现在是 SAP）复制服务器 (SRS) 可以在 Sybase/SAP ASE 表之间复制时间戳值，即 SRS 维护用户可以将显式值插入到类型为 timestamp 的列中。

这怎么可能？有几个要求：

• 执行插入（到timestamp 列）的用户必须具有replication_role 角色（并且必须处于活动状态）
• 您需要发出set timestamp_insert on 命令（注意：如果您的用户没有replication_role，这将产生错误）
• 您需要在插入语句中显式列出目标表的列

设置：

exec sp_displaylogin
go
...
Configured Authorization:
        ...
        replication_role (default ON)      <<<=== verify role assigned and active
        ...

create table EX_EMPLOYEE
(NAME_X                 varchar(10)     NULL
,RECORD_TIME_STAMP      timestamp       NULL
)
go

insert into EX_EMPLOYEE (NAME_X) values ('Larry')
insert into EX_EMPLOYEE (NAME_X) values ('Mo')
insert into EX_EMPLOYEE (NAME_X) values ('Curly')
go

select * from EX_EMPLOYEE
go

 NAME_X     RECORD_TIME_STAMP
 ---------- ------------------
 Larry      0x00000000ec4304fa
 Mo         0x00000000ec4304fd
 Curly      0x00000000ec430501

select * into EX_EMPLOYEE_T FROM EX_EMPLOYEE where 1=2
go

现在进行一些插入测试...

-- haven't issued the 'set timestamp_insert on' commmand, yet

insert into EX_EMPLOYEE_T
select * from EX_EMPLOYEE
go

Warning: A non-null value cannot be inserted into a TIMESTAMP column by the user. The database timestamp value has been inserted into the TIMESTAMP field instead.

-- received the *WARNING*, ie, rows are inserted but they receive new timestamp values

select * from EX_EMPLOYEE_T
go

 NAME_X     RECORD_TIME_STAMP
 ---------- ------------------
 Larry      0x00000000ec430548       <<<=== different from what's in EX_EMPLOYEE
 Mo         0x00000000ec43054a       <<<=== different from what's in EX_EMPLOYEE
 Curly      0x00000000ec43054c       <<<=== different from what's in EX_EMPLOYEE

-- enable direct insert of timestamp values

set timestamp_insert on
go

truncate table EX_EMPLOYEE_T
go

-- w/out explicitly listing target columns ...

insert into EX_EMPLOYEE_T
select * from EX_EMPLOYEE
go

-- no warning message is generated, insert succeeds, but new timestamp values are generated

select * from EX_EMPLOYEE_T
go

 NAME_X     RECORD_TIME_STAMP
 ---------- ------------------
 Larry      0x00000000ec430555       <<<=== different from what's in EX_EMPLOYEE
 Mo         0x00000000ec430557       <<<=== different from what's in EX_EMPLOYEE
 Curly      0x00000000ec430559       <<<=== different from what's in EX_EMPLOYEE

truncate table EX_EMPLOYEE_T
go

-- this time we'll explicitly list the target table's columns ...

insert into EX_EMPLOYEE_T (NAME_X, RECORD_TIME_STAMP)
select * from EX_EMPLOYEE
go

-- and now we see the timestamp values copied from the source

select * from EX_EMPLOYEE_T
go

 NAME_X     RECORD_TIME_STAMP
 ---------- ------------------
 Larry      0x00000000ec4304fa       <<<=== same as what's in EX_EMPLOYEE
 Mo         0x00000000ec4304fd       <<<=== same as what's in EX_EMPLOYEE
 Curly      0x00000000ec430501       <<<=== same as what's in EX_EMPLOYEE

以上是在 ASE 15.7 SP138 数据服务器上测试的。