cds.RecordCount 问题
cds.RecordCount 有问题吗？
我通常用它来确定查询中是否有任何记录。
但他在与一所大学交谈时表示，这样做会降低成绩！
我做了一些测试，没有发现什么重大问题。
那么 RecordCount 是否存在性能损失或任何其他问题？！
如果是这样，检查查询中是否有某些记录的最佳方法是什么？
谢谢
Is there a problem with cds.RecordCount ?
I usually use it to determine if I have any records in a query.
But talking with a college he told that there is a performance penalty to that!
I have made some test and nothing major came up.
So is there a performance penalty or any other problem with RecordCount?!
If so, what is the best way to check if there are some records in a query?
Thanks
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如果您使用 TClientDataSet（正如您的“cds”似乎暗示的那样），并将
PacketRecords设置为-1（默认）或将FetchOnDemand设置为False没有区别，因为客户端数据集会立即接收所有数据并将其加载到内存中。对于其他数据集来说，差异是显而易见的，这些数据集在您前进光标时按需获取数据，使用
RecordCount将首先获取所有数据。在这种情况下，如果您只想知道结果集是否为空，最好在打开后使用数据集的EOF属性。If you're using TClientDataSet (as your 'cds' seems to imply) with
PacketRecordsset to-1(default) orFetchOnDemandset toFalsethere is no difference since the client dataset receives and loads all data into memory at once.The difference would be noticable with other datasets which fetch data on demand as you advance the cursor, using
RecordCountwould fetch all data first. In such cases it's better to use the dataset'sEOFproperty after opening - if all you want to know is whether the result set was empty or not.最好的解决方案是执行
SELECT COUNT(*)查询。如果您需要本地所有记录，则应将
FetchOnDemand属性设置为False，或者您可以在cds 之前调用cds.Last。记录计数。如果目的是检查数据集是否包含记录，还有一个 cds.IsEmpty 方法...
The best solution would be to execute a
SELECT COUNT(*)query.If you need all records locally, you should set the
FetchOnDemandproperty toFalseor you can callcds.Lastright beforecds.RecordCount.There is also a
cds.IsEmptymethod if the purpose is to check whether the dataset contains records...