自动递增主键值始终为0 [英] Auto increment primary key value is always 0

问题描述

我正尝试使用以下代码向数据库添加新行.

I was trying to add a new row to the database using the below code.

即使Rundef表具有应自动递增的主键，其值始终为零.为什么会这样?

Even though the Rundef table has a primary key that should auto increment, it's value is always zero. Why does this happen?

Private oRunDefDS As DataSet
Dim oDR As DataRow = oRunDefDS.Tables("RunDef").NewRow()

Rundef表的设计:

推荐答案

在代码中创建新行时，尚未将其插入数据库中.这意味着数据库引擎尚未分配其增量ID，而是将其默认设置为0.

When you create a new row in code it hasn't been inserted into the database yet. This means the database engine hasn't assigned it's incremental ID and gives it a default of 0 instead.

将记录插入数据库，并且ID应该自动更新，尽管您可能还需要重新读取该行以取回数据，具体取决于您使用的数据访问方式.

Insert the record to the database and the id should be updated automatically, though you might need to re-read the row to get the data back depending on the data access too you are using.

如果不是这种情况，那么您的代码可以创建许多新行，仅供内部使用，但是需要对所使用的ID进行保留.如果您从未将这些新行保存到数据库中，您的增量ID最终将有很多空白.

If this were not the case then your code could create many new rows for internal use only, but there would need to be a reservation on the IDs used. If you never saved these new row to the database you would end up with lots of gaps in your incremental IDs.

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