sql-server - SQL Server 转换因算术溢出而失败

Question

根据SQL Server 2008联机丛书中关于小数和数字数据类型的条目，精度为:

p (precision) The maximum total number of decimal digits that can be stored, both to the left and to the right of the decimal point. The precision must be a value from 1 through the maximum precision of 38. The default precision is 18.

但是，下面的第二个选择失败，出现“将 int 转换为数字数据类型时出现算术溢出错误。”

SELECT CAST(123456789 as decimal(9,0))
SELECT CAST(123456789 as decimal(9,1))

Answer 1

看这里:http://msdn.microsoft.com/en-us/library/aa258832(SQL.80).aspx

decimal[(p[, s])]

p (precision) Specifies the maximum total number of decimal digits that can be stored, both to the left and to the right of the decimal point. The precision must be a value from 1 through the maximum precision. The maximum precision is 38. The default precision is 18.

s (scale) Specifies the maximum number of decimal digits that can be stored to the right of the decimal point. Scale must be a value from 0 through p. Scale can be specified only if precision is specified. The default scale is 0; therefore, 0 <= s <= p. Maximum storage sizes vary, based on the precision.

当使用:decimal(p,s) 时，将p 视为您要存储的总位数(无论小数点左边还是右边) , 和 s 作为这些 p 数字中有多少应该在小数点的右边。

DECIMAL(10,5)=     12345.12345
DECIMAL(10,2)=  12345678.12
DECIMAL(10,10)=         .1234567891
DECIMAL(11,10)=        1.1234567891

您的示例代码失败了:

SELECT CAST(123456789 as decimal(9,1))

因为:

9=精度(小数点左右的总位数)
1=scale(小数点右边的总位数)
(9-1)=8(小数点左边的总位数)

您的值 123456789 需要小数点左边的 9 位数字。你将需要 decimal(10,1) 或者只是 decimal(9,0)