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Overview

LN() will return the exponential value of its argument, which is recognized as the input parameter’s natural logarithm.
Info:
The logarithm doesn’t take negative numbers or 0.

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*yntax

The syntax of the LN() function is described as follows. 
LN (x)
x:  A positive or a negative number (or an expression that evaluates to a number).

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Examples

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Case #1: Basic LN() function

The example below shows that LN() function will return the natural logarithm of the number 7,87653. 
SELECT LN(7.87653);
The final result is as follows. 
+-------------+
| f           |
+-------------+
| 2.0638874   |
+-------------+

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Case #2: Using LN() Function With a Table

In the following example, we will combine LN() function with CREATE TABLE statement. Therefore we can obtain natural logarithmic values of a specific column.
  1. Create a new table named LNTable containing the initValue column with an integer value.
CREATE TABLE LNtable(initValue int);
INSERT INTO LNtable(initValue)
VALUES (75), (18), (28);
  1. Run the following query to get the logarithm output of the column:
SELECT * ,LN(initValue) AS lnValue FROM LNtable;
  1. It will return the initial value with its natural logarithm value.
  • initValue column with the initial integer values.
  • lnValue column with the natural logarithm values.
+------------+---------------------------+
| initValue  | lnValue                   |
+------------+---------------------------+
| 75         | 4.31748811353631          |
| 18         | 2.8903717578961645        |
| 28         | 3.332204510175204         |
+------------+---------------------------+