log-transact-sql.md

title	description	author	ms.author	ms.date	ms.service	ms.subservice	ms.topic	f1_keywords	helpviewer_keywords	dev_langs	monikerRange
LOG (Transact-SQL)	LOG (Transact-SQL)	markingmyname	maghan	07/29/2017	sql	t-sql	reference	LOG LOG_TSQL	float expressions logarithm of expression LOG function	TSQL	>= aps-pdw-2016 || = azuresqldb-current || = azure-sqldw-latest || >= sql-server-2016 || >= sql-server-linux-2017 || = azuresqldb-mi-current||=fabric

LOG (Transact-SQL)

[!INCLUDE sql-asdb-asdbmi-asa-pdw-fabricse-fabricdw]

Returns the natural logarithm of the specified float expression in [!INCLUDEssNoVersion].

:::image type="icon" source="../../includes/media/topic-link-icon.svg" border="false"::: Transact-SQL syntax conventions

Syntax

-- Syntax for SQL Server, Azure SQL Database  
  
LOG ( float_expression [, base ] )  

-- Syntax for Azure Synapse SQL 
  
LOG ( float_expression )  

Arguments

float_expression
Is an expression of type float or of a type that can be implicitly converted to float.

base
Optional integer argument that sets the base for the logarithm.

Applies to: [!INCLUDEssSQL11] and later

Return Types

float

Remarks

By default, LOG() returns the natural logarithm. Starting with [!INCLUDEssSQL11], you can change the base of the logarithm to another value by using the optional base parameter.

The natural logarithm is the logarithm to the base e, where e is an irrational constant approximately equal to 2.718281828.

The natural logarithm of the exponential of a number is the number itself: LOG( EXP( n ) ) = n. And the exponential of the natural logarithm of a number is the number itself: EXP( LOG( n ) ) = n.

Examples

A. Calculating the logarithm for a number.

The following example calculates the LOG for the specified float expression.

DECLARE @var FLOAT = 10;  
SELECT 'The LOG of the variable is: ' + CONVERT(VARCHAR, LOG(@var));  
GO  

[!INCLUDEssResult]

-------------------------------------  
The LOG of the variable is: 2.30259  
  
(1 row(s) affected)  

B. Calculating the logarithm of the exponent of a number.

The following example calculates the LOG for the exponent of a number.

SELECT LOG (EXP (10));  
  

[!INCLUDEssResult]

----------------------------------  
10  
(1 row(s) affected)  

Examples: [!INCLUDEssazuresynapse-md] and [!INCLUDEssPDW]

C. Calculating the logarithm for a number

The following example calculates the LOG for the specified float expression.

SELECT LOG(10);  

[!INCLUDEssResult]

----------------`  
 
2.30

See Also

Mathematical Functions (Transact-SQL)
EXP (Transact-SQL)
LOG10 (Transact-SQL)