LOG (Azure Cosmos DB)LOG (Azure Cosmos DB)

适用于: SQL API

返回指定数值表达式的自然对数。Returns the natural logarithm of the specified numeric expression.


LOG (<numeric_expr> [, <base>])  


是一个数值表达式。Is a numeric expression.

可选的数值参数,用于设置对数的底。Optional numeric argument that sets the base for the logarithm.

返回类型Return types

返回一个数值表达式。Returns a numeric expression.


默认情况下,LOG() 返回自然对数。By default, LOG() returns the natural logarithm. 可以通过使用可选的 base 参数将对数的底更改为其他值。You can change the base of the logarithm to another value by using the optional base parameter.

自然对数是以 e 为底的对数,其中,e 是一个无理常量,约等于 2.718281828。The natural logarithm is the logarithm to the base e, where e is an irrational constant approximately equal to 2.718281828.

数字的指数的自然对数是数字本身:LOG( EXP( n ) ) = n。The natural logarithm of the exponential of a number is the number itself: LOG( EXP( n ) ) = n. 以及数字的自然对数的指数是数字本身:EXP( LOG( n ) ) = n。And the exponential of the natural logarithm of a number is the number itself: EXP( LOG( n ) ) = n.

此系统函数不会使用索引。This system function will not utilize the index.


以下示例声明一个变量并返回指定变量 (10) 的对数值。The following example declares a variable and returns the logarithm value of the specified variable (10).

SELECT LOG(10) AS log  

下面是结果集。Here is the result set.

[{log: 2.3025850929940459}]  

以下示例计算某个数字的指数的 LOGThe following example calculates the LOG for the exponent of a number.

SELECT EXP(LOG(10)) AS expLog  

下面是结果集。Here is the result set.

[{expLog: 10.000000000000002}]  

后续步骤Next steps