Float and Real
Approximate-number data types for use with floating point numeric data. Floating point data is approximate; therefore, not all values in the data type range can be represented exactly. The ISO synonym for real is float(24).
| Data type | Range | Storage |
|---|---|---|
float |
- 1.79E+308 to -2.23E-308, 0 and 2.23E-308 to 1.79E+308 |
Depends on the value of n |
real |
- 3.40E + 38 to -1.18E - 38, 0 and 1.18E - 38 to 3.40E + 38 |
4 Byt |
float [ ( n ) ]
-
Where n is the number of bits that are used to store the mantissa of the float number in scientific notation and, therefore, dictates the precision and storage size. If n is specified, it must be a value between 1 and 53. The default value of n is 53.
n value Precision Storage size 1-24
7 digits
4 bytes
25-53
15 digits
8 bytes
Decimal and Numeric
Numeric data types that have fixed precision and scale.
- [ ( p[ , s] )] and numeric[ ( p[ , s] )]
-
are dec and dec(p, s). numeric is functionally equivalent to decimal.
- (scale)
-
. 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.
decimalFixed precision and scale numbers. When maximum precision is used, valid values are from - 10^38 +1 through 10^38 - 1. The ISO synonyms for decimalp (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.s 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
Money and SmallMoney
Data types that represent monetary or currency values.
| Data type | Range | Storage | |
|---|---|---|---|
money |
-922,337,203,685,477.5808 to 922,337,203,685,477.5807 |
8 bytes |
|
smallmoney |
- 214,748.3648 to 214,748.3647 |
4 bytes |
decimal建议在数据较大，或要求精度较高，或对计算结果进行精度控制时使用。decimal和numeric基本没有什么不同。