SQL Server RowVersion / Timestamp - 比较 [英] SQL Server RowVersion/Timestamp - Comparisons

问题描述

我知道 RowVersion 列的值本身不是有用的，除非它每次更新行时都会更改。

I know that the value itself for a RowVersion column is not in and of itself useful, except that it changes each time the row is updated. However, I was wondering if they are useful for relative (inequality) comparison.

如果我有一个有 RowVersion column：

If I have a table with a RowVersion column, are either of the following true:

• 同时发生的所有更新（同一更新语句或同一事务）在 RowVersion 列中有相同的值吗？


• 如果我更新A，然后更新B在更新B中具有比更新A中涉及的行更高的值？

• Will all updates that occur simultaneously (either same update statement or same transaction) have the same value in the RowVersion column?
• If I do update "A", followed by update "B", will the rows involved in update "B" have a higher value than the rows involved in update "A"?

$ b

推荐答案

从MSDN ：

From MSDN:

每个数据库的计数器对于每次插入或更新在数据库中包含 rowversion 列的表。这个计数器是数据库 rowversion 。这跟踪数据库中的相对时间，而不是跟时钟相关联的实际时间。 每次已修改或插入 在 rowversion 列中插入增量数据库 rowversion

Each database has a counter that is incremented for each insert or update operation that is performed on a table that contains a rowversion column within the database. This counter is the database rowversion. This tracks a relative time within a database, not an actual time that can be associated with a clock. Every time that a row with a rowversion column is modified or inserted, the incremented database rowversion value is inserted in the rowversion column.

http://msdn.microsoft.com /en-us/library/ms182776.aspx

• 据我所知，系统中没有同时发生的动作。这意味着所有 rowversion s应该是唯一的。我冒昧地说，如果在同一个表内允许重复，它们实际上是无用的。还给予 rowversion 不重复的信任是MSDN的不使用它们作为主键的立场，不是因为它会导致违反，而是因为它会导致外键问题。 li>
  
• 根据MSDN，rowversion数据类型只是一个递增的数字...所以是，后来更大。

• As far as I understand, nothing ACTUALLY happens simultaneously in the system. This means that all rowversions should be unique. I venture to say that they would be effectively useless if duplicates were allowed within the same table. Also giving credance to rowversions not being duplicated is MSDN's stance on not using them as primary keys not because it would cause violations, but because it would cause foreign key issues.
• According to MSDN, "The rowversion data type is just an incrementing number..." so yes, later is larger.

对于增加的问题，MSDN指出：[ rowversion ]跟踪数据库中的相对时间这表示它不是一个流体整数递增，而是基于时间。但是，这个时间在确切时不显示任何内容，而是在相对于其他行插入/修改行。

To the question of how much it increments, MSDN states, "[rowversion] tracks a relative time within a database" which indicates that it is not a fluid integer incrementing, but time based. However, this "time" reveals nothing of when exactly, but rather when in relation to other rows a row was inserted/modified.

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