哪种 .NET 数据类型最适合在 NHibernate 中映射 NUMBER Oracle 数据类型？
我见过一些在 NHibernate 项目中使用十进制来映射到 Oracle 中的整数列的示例。现在我在程序中使用 int 和 long 。
decimal 相对于 int/long 有哪些优势？它的性能更好吗？
I've seen some examples in which decimal is used in NHibernate projects for mapping to whole number columns in Oracle. Right now I'm using int and long in my program.
What are the advantages of decimal over int/long? Does it perform better?
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这可能是因为 .NET
decimal和 OracleNUMBER映射比long和NUMBER更好一点，而且还为您提供了更大的灵活性。如果您稍后在 Oracle 列中添加小数位数，那么如果您已经使用了十进制，则无需更改数据类型。decimal肯定比int和long慢，因为硬件支持后两者。也就是说，您必须处理大量数据才能发挥作用。我仍然认为您应该使用long如果这就是您正在处理的内容，那么您还应该让表列定义来表示它。NUMBER(18,0)表示long等等。decimal映射得更好一点的原因是long是 64 位，而decimal是（某种）128 位。.NET
Oracle
NUMBER默认为 38 位有效数字，小数位数为 0（整数）。Microsoft 已意识到该问题并注释
想想看，您实际上需要
BigInteger能够表示与NUMBER默认值相同的有效数字。我从未见过有人这样做，我认为这是一个非常罕见的需求。而且BigInteger仍然不会削减它，因为NUMBER可以是正无穷大和负无穷大。That's probably because .NET
decimaland OracleNUMBERmaps a bit better thanlongandNUMBERand it also gives you more flexibility. If you at a later stage add a scale in the Oracle column then you wouldn't have to change datatype if you already useddecimal.decimalis certainly slower thanintandlongsince the later two are supported in hardware. That said, you have to crunch some serious amount of data for it to make any difference. I still think that you should uselongif that that's what you're dealing with and then you should also let the table column definitions represent that.NUMBER(18,0)forlongand so on.The reason
decimalmaps a little better is thatlongis 64 bits anddecimalis (kind of) 128 bits..NET
Oracle
NUMBERdefaults to 38 significant digits and scale 0 (integer).Microsoft is aware of the problem and notes
Come to think of it you actually need
BigIntegerto be able to represent the same number of significant digits as to whatNUMBERdefaults to. I've never seen anyone do that and I would suppose it's a very rare need. AlsoBigIntegerstill wouldn't cut it sinceNUMBERcan be of positive and negative infinity.