作为对其他答案主旨的反驳。看金钱的诸多好处…数据类型!在SQLCAT的关系引擎指南中

我要具体指出以下几点

Working on customer implementations, we found some interesting performance numbers concerning the money data type. For example, when Analysis Services was set to the currency data type (from double) to match the SQL Server money data type, there was a 13% improvement in processing speed (rows/sec). To get faster performance within SQL Server Integration Services (SSIS) to load 1.18 TB in under thirty minutes, as noted in SSIS 2008 - world record ETL performance, it was observed that changing the four decimal(9,2) columns with a size of 5 bytes in the TPC-H LINEITEM table to money (8 bytes) improved bulk inserting speed by 20% ... The reason for the performance improvement is because of SQL Server’s Tabular Data Stream (TDS) protocol, which has the key design principle to transfer data in compact binary form and as close as possible to the internal storage format of SQL Server. Empirically, this was observed during the SSIS 2008 - world record ETL performance test using Kernrate; the protocol dropped significantly when the data type was switched to money from decimal. This makes the transfer of data as efficient as possible. A complex data type needs additional parsing and CPU cycles to handle than a fixed-width type.

所以这个问题的答案是“视情况而定”。对于某些算术操作，您需要更加小心，以保持精度，但您可能会发现，出于性能考虑，这样做是值得的。

永远不要使用金钱。它不精确，纯粹是垃圾;总是使用十进制/数字。

运行这个来看看我的意思:

DECLARE
    @mon1 MONEY,
    @mon2 MONEY,
    @mon3 MONEY,
    @mon4 MONEY,
    @num1 DECIMAL(19,4),
    @num2 DECIMAL(19,4),
    @num3 DECIMAL(19,4),
    @num4 DECIMAL(19,4)

    SELECT
    @mon1 = 100, @mon2 = 339, @mon3 = 10000,
    @num1 = 100, @num2 = 339, @num3 = 10000

    SET @mon4 = @mon1/@mon2*@mon3
    SET @num4 = @num1/@num2*@num3

    SELECT @mon4 AS moneyresult,
    @num4 AS numericresult

输出:2949.0000 2949.8525

有些人说钱不能一分一分

这是我计算相关性的一个问题，把它换成金钱会得到错误的结果。

select t1.index_id,t2.index_id,(avg(t1.monret*t2.monret)
    -(avg(t1.monret) * avg(t2.monret)))
            /((sqrt(avg(square(t1.monret)) - square(avg(t1.monret))))
            *(sqrt(avg(square(t2.monret)) - square(avg(t2.monret))))),
current_timestamp,@MaxDate
            from Table1 t1  join Table1 t2  on t1.Date = traDate
            group by t1.index_id,t2.index_id

我们刚刚遇到了一个非常相似的问题，我现在非常+1，因为除了在顶级演示中，我从不使用Money。我们有多个表(实际上是一个销售凭证和一个销售发票)，由于历史原因，每个表都包含一个或多个Money字段，我们需要按比例计算出总发票中有多少Tax与销售凭证上的每一行相关。我们的计算是

vat proportion = total invoice vat x (voucher line value / total invoice value)

这将导致现实世界中的货币/货币计算，从而导致在分割部分上的刻度错误，然后乘以一个不正确的增值税比例。当这些价值随后相加时，我们最终得到的是增值税比例的总和，加起来不等于发票总价值。如果括号中的任何一个值是小数(我将把其中一个转换为小数)，vat比例将是正确的。

当括号不存在的时候，原来这是工作的，我猜是因为涉及到更大的值，它有效地模拟了一个更高的规模。我们添加括号是因为它先做乘法运算，这在一些罕见的情况下会破坏计算的精度，但这现在已经导致了这个更常见的错误。

作为对其他答案主旨的反驳。看金钱的诸多好处…数据类型!在SQLCAT的关系引擎指南中

我要具体指出以下几点

Working on customer implementations, we found some interesting performance numbers concerning the money data type. For example, when Analysis Services was set to the currency data type (from double) to match the SQL Server money data type, there was a 13% improvement in processing speed (rows/sec). To get faster performance within SQL Server Integration Services (SSIS) to load 1.18 TB in under thirty minutes, as noted in SSIS 2008 - world record ETL performance, it was observed that changing the four decimal(9,2) columns with a size of 5 bytes in the TPC-H LINEITEM table to money (8 bytes) improved bulk inserting speed by 20% ... The reason for the performance improvement is because of SQL Server’s Tabular Data Stream (TDS) protocol, which has the key design principle to transfer data in compact binary form and as close as possible to the internal storage format of SQL Server. Empirically, this was observed during the SSIS 2008 - world record ETL performance test using Kernrate; the protocol dropped significantly when the data type was switched to money from decimal. This makes the transfer of data as efficient as possible. A complex data type needs additional parsing and CPU cycles to handle than a fixed-width type.

所以这个问题的答案是“视情况而定”。对于某些算术操作，您需要更加小心，以保持精度，但您可能会发现，出于性能考虑，这样做是值得的。

SQLMenace说钱是不精确的。但是你不能把钱乘以/除以钱!3美元乘以50美分等于多少?150 dollarcents ?你用标量乘(除)钱，结果应该是小数。

DECLARE
@mon1 MONEY,
@mon4 MONEY,
@num1 DECIMAL(19,4),
@num2 DECIMAL(19,4),
@num3 DECIMAL(19,4),
@num4 DECIMAL(19,4)

SELECT
@mon1 = 100,
@num1 = 100, @num2 = 339, @num3 = 10000

SET @mon4 = @mon1/@num2*@num3
SET @num4 = @num1/@num2*@num3

SELECT @mon4 AS moneyresult,
@num4 AS numericresult

结果在正确的结果:

moneyresult           numericresult
--------------------- ---------------------------------------
2949.8525             2949.8525

钱是好的，只要你不需要超过4个十进制数字，你要确保你的标量(不代表钱)是小数。

如果你不知道自己在做什么，一切都是危险的

即使是高精度的十进制类型也无法扭转局面:

declare @num1 numeric(38,22)
declare @num2 numeric(38,22)
set @num1 = .0000006
set @num2 = 1.0
select @num1 * @num2 * 1000000

1.000000 <-应该是0.6000000

货币类型是整数

smallmoney和decimal(10,4)的文本表示可能看起来很像，但这并不意味着它们可以互换。当您看到日期存储为varchar(10)时，您会感到畏缩吗?这是一样的。

在幕后，money/smallmoney只是一个bigint/int。money的文本表示中的小数点在视觉上是无用的，就像yyyy-mm-dd日期中的破折号。SQL实际上并没有在内部存储这些数据。

关于十进制和金钱，选择任何适合你需要的。货币类型的存在是因为将会计值存储为单位的1/ 10000000的整数倍数是非常常见的。此外，如果您正在处理实际的货币和计算，而不仅仅是简单的加减法，那么您不应该在数据库级别上这样做!在应用程序级别使用支持Banker's舍入的库进行计算(IEEE 754)