POWER (Transact-SQL)

Artykuł
12/08/2014

Returns the value of the specified expression to the specified power.

Ikona łącza do tematu Transact-SQL Syntax Conventions

Składnia

POWER ( float_expression , y )

Arguments

float_expression
Is an expression of type float or of a type that can be implicitly converted to float.
y
Is the power to which to raise float_expression. y can be an expression of the exact numeric or approximate numeric data type category, except for the bit data type.

Return Types

Returns the same type as submitted in float_expression. For example, if a decimal(2,0) is submitted as float_expression, the result returned is decimal(2,0).

Examples

A. Using POWER to return the cube of a number

The following example demonstrates raising a number to the power of 3 (the cube of the number).

DECLARE @input1 float;
DECLARE @input2 float;
SET @input1= 2;
SET @input2 = 2.5;
SELECT POWER(@input1, 3) AS Result1, POWER(@input2, 3) AS Result2;

Here is the result set.

Result1                Result2
---------------------- ----------------------
8                      15.625

(1 row(s) affected)

B. Using POWER to show results of data type conversion

The following example shows how the float_expression preserves the data type which can return unexpected results.

SELECT 
POWER(CAST(2.0 AS float), -100.0) AS FloatResult,
POWER(2, -100.0) AS IntegerResult,
POWER(CAST(2.0 AS int), -100.0) AS IntegerResult,
POWER(2.0, -100.0) AS Decimal1Result,
POWER(2.00, -100.0) AS Decimal2Result,
POWER(CAST(2.0 AS decimal(5,2)), -100.0) AS Decimal2Result;
GO

Here is the result set.

FloatResult            IntegerResult IntegerResult Decimal1Result Decimal2Result Decimal2Result
---------------------- ------------- ------------- -------------- -------------- --------------
7.88860905221012E-31   0             0             0.0            0.00           0.00

C. Using POWER

The following example returns POWER results for 2.

DECLARE @value int, @counter int;
SET @value = 2;
SET @counter = 1;

WHILE @counter < 5
   BEGIN
      SELECT POWER(@value, @counter)
      SET NOCOUNT ON
      SET @counter = @counter + 1
      SET NOCOUNT OFF
   END;
GO

Here is the result set.

----------- 
2           

(1 row(s) affected)

----------- 
4           

(1 row(s) affected)

----------- 
8           

(1 row(s) affected)

----------- 
16          

(1 row(s) affected)