Transact-SQL Syntax ConventionsApproximate-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).
Transact-SQL Syntax Conventions
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 |
[!NOTE]
SQL Server treats n as one of two possible values. If 1<=n<=24, n is treated as 24. If 25<=n<=53, n is treated as 53.
The SQL Server float[(n)] data type complies with the ISO standard for all values of n from 1 through 53. The synonym for double precision is float(53).
| 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 Bytes |
Values of float are truncated when they are converted to any integer type.
When you want to convert from float or real to character data, using the STR string function is usually more useful than CAST( ). This is because STR enables more control over formatting. For more information, see STR (Transact-SQL) and Functions (Transact-SQL).
Conversion of float values that use scientific notation to decimal or numeric is restricted to values of precision 17 digits only. Any value < 5E-18 rounds down to 0.
ALTER TABLE (Transact-SQL)
CAST and CONVERT (Transact-SQL)
CREATE TABLE (Transact-SQL)
Data Type Conversion (Database Engine)
Data Types (Transact-SQL)
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