SQL LOG Function

The SQL LOG function is one of the Mathematical function which is used to calculate the natural logarithmic value of given float value. In this article we will show you, How to use SQL Server LOG function with example.

SQL LOG Function Syntax

The basic syntax of the SQL Server LOG Function is as shown below:

SELECT LOG (Float_Expression, base)
FROM [Source]

Base: This is an optional argument. If you omit this argument, SQL LOG function will consider the default e as logarithm base. However, you can change the base value as per your requirement. The value of e is approximately equal to 2.71828

SQL LOG Function Example 1

The SQL LOG Function is used to calculate the logarithmic value of given number with specified base value. In this example, We are going to check the same with different data and display the output

T-SQL CODE

DECLARE @i float
SET @i = 10

SELECT LOG(@i)AS [LOG Result 1]

-- Calculating LOG directly
SELECT LOG(1) AS [LOG Result 2]

SELECT LOG(96) AS [LOG Result 3]

SELECT LOG(10.90 + 15.10 - 22.50 + 1.50) AS [LOG Result 4]

-- Calculating LOG with two arguments
SELECT LOG(10, 4) AS [LOG Result 5]

SELECT LOG((10.90 + 15.10 - 22.50 + 1.50), 8) AS [LOG Result 6]

OUTPUT

ANALYSIS

Within this log function example query, the below lines of code is used to declare float variable and assigning the value.

DECLARE @i float
SET @i = 10

Next, we are calculating the logarithmic value of @i base e (It means LOG(10, e)). We also assigned new name to the result as ‘LOG Result 1’ using SQL ALIAS Column.

SELECT LOG(@i)AS [LOG Result 1]

In the below statement, We used LOG function directly on the float values

SELECT LOG(1) AS [LOG Result 2]
SELECT LOG(96) AS [LOG Result 3]
SELECT LOG(10.90 + 15.10 - 22.50 + 1.50) AS [LOG Result 4]

In the next statement, We used the LOG Function with two arguments (float and base value). It means logarithmic value of 10 base 4.

SELECT LOG(10, 4) AS [LOG Result 5]

SQL LOG Function Example 2

In this example, We are going to calculate the logarithmic value of all the records present in the [StandardCost] and [Tax Amount] using LOG Function.

T-SQL CODE

SELECT [EnglishProductName]
      ,[Color]
      ,[StandardCost]
      ,LOG([StandardCost], 8) AS [Cost_Log result]
      ,[ListPrice]
      ,[DealerPrice]
      ,[SalesAmount]
      ,[TaxAmt]
      ,LOG([TaxAmt]) AS [Tax_Log result]
  FROM [SQL Tutorial].[dbo].[Prod Sales]

OUTPUT

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