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SQL Server rowversion 不添加列

[英]SQL Server rowversion without adding a column

原文 2017-10-30 21:35:09 4 1 sql/ sql-server/ versioning

Typically to expose version data you'd have to add a column of type rowversion , but this operation would take quite a while on a large table.通常要公开版本数据，您必须添加一个rowversion类型的rowversion ，但此操作在大表上需要很rowversion 。 I did it anyway in a dev sandbox environment, and indeed it took a while, but I also noticed that the column was populated with some meaningful-looking initial value.无论如何，我是在开发沙盒环境中完成的，确实花了一段时间，但我也注意到该列填充了一些看起来有意义的初始值。 I expected it to be all 0's or 1's to indicate that each row is in some sort of "initial" state (after all, there was no history before this), but what I saw were what looked like accurate values for each row (they were all different, non-default-looking values).我希望它全是 0 或 1 来表示每一行都处于某种“初始”状态（毕竟，在此之前没有历史记录），但我看到的是每一行的准确值（它们都是不同的、非默认值）。

Where did they come from?哪儿来的？ It seems like the rowversion is being tracked behind the scenes anyway, regardless of whether you've exposed it in a column.无论如何，无论您是否在列中公开它，似乎rowversion都在幕后进行跟踪。 If so, can I get at it directly without adding the column?如果是这样，我可以在不添加列的情况下直接获取它吗？ Like maybe some kind of system function I can call directly?就像我可以直接调用的某种系统函数一样？ I really want to avoid downtime, and I also have a huge number of existing queries so migration to a different table/view/combo is not an option (as suggested in other related questions).我真的很想避免停机，而且我还有大量现有查询，因此迁移到不同的表/视图/组合不是一种选择（如其他相关问题中所建议的那样）。

1 个解决方案

The rowversion value is generated when a table with a rowversion (aka timestamp ) value is modified. rowversion值是在修改具有rowversion （又名timestamp ）值的表时生成的。 The rowversion value is database-scoped and the last generated value can be retrieved via @@DBTS . rowversion值是数据库范围的，最后生成的值可以通过@@DBTS检索。

Since the value is incremented only when a rowversion table is modified, I don't think you'll be able to use @@DBTS to avoid the downtime.由于仅在修改 rowversion 表时才会增加该值，因此我认为您无法使用@@DBTS来避免停机。