# MySQL LN() Function – Easily find the natural logarithm of a number in MySQL

In this tutorial, we will learn about the MySQL `LN()` function. While studying maths, you must have come across the operation – loge (logarithm to the base of the mathematical constant e). Finding the loge of a number is also known as finding the natural logarithm of a number.

Logarithm, in general, is a widely used operation across many fields, and therefore, MySQL provides us with the `LN()` function.

The `LN()` function in MySQL is a mathematical function which is used to find the natural logarithm of a number. The `LN()` function is the inverse of the `EXP()` function. Let us explore the `LN()` function now.

## Syntax of MySQL LN() function

```LN(number);
```

Where â€˜numberâ€™ is a number greater than 0 whose natural logarithm is to be found out.

## Examples of MySQL LN() function

Let us start with some basic examples. How about finding the values of loge 2, loge 10 and loge 32 using the `LN()` function. The queries for these operations are –

```SELECT LN(2);
SELECT LN(10);
SELECT LN(32);
```

And we get the output as,

### MySQL LN() With Zero and NULL

I mentioned earlier that the â€˜numberâ€™ argument passed to the `LN()` function should be greater than 0. So what if you pass zero or NULL to the `LN()` function? In such a case, the `LN()` function will return NULL. Let us demonstrate this using the below queries.

```SELECT LN(0);
SELECT LN(NULL);
```

And the output is,

### MySQL LN() With Negative Numbers

As you saw in the previous example, `LN()` returns NULL if the argument is 0 or NULL. `MySQL LN()` shows the same behavior when we pass a negative number as its parameter. Let us see this behavior using the below examples.

```SELECT LN(-5);
SELECT LN(-2);
```

And we get the output as,

### LN() With Expressions

Let us now use expressions with `MySQL LN()`. Consider the below query.

```SELECT LN(3+3), LN(6);
```

Both expressions will output the same result as shown below.

Let us now find the result of the following expression using the LN() function – loge 23. The query is,

```SELECT LN(POW(2, 3));
```

And the output is,

### How are LN() and EXP() related?

`LN()` is the inverse of the `EXP()` function. Let us see this using the below example. How about finding the natural logarithm of e? We do so using the below query.

```SELECT LN(EXP(1)) AS 'ln(e)';
```

And the output is,

As you can see, the output is 1, which is the number we passed as the argument. This shows that `LN()` is the inverse of `EXP()`. Letâ€™s see a couple more examples before we move on to the next topic. Consider the following expressions – loge e2 and loge e55. The queries are –

```SELECT LN(EXP(2));
SELECT LN(EXP(55));
```

And the output is,

## Using LN() With Tables

Consider the below Numbers table.

### Simple Example

Letâ€™s kick things off with a simple example by finding the natural logarithm of all values in the X column. The query is,

```SELECT LN(X) FROM Numbers;
```

And we get the output as,

### LN() With the UPDATE statement

With reference to the previous example, let us create a new column named `LN_Of_X` in the â€˜Numbersâ€™ table which contains the natural logarithm values of the values in the `X` column. The queries for this are –

```ALTER TABLE Numbers ADD LN_Of_X float;
UPDATE Numbers SET LN_Of_X=LN(X);
SELECT * FROM Numbers;
```

We use the `ALTER` statement to add the `LN_Of_X` column of data type float to the Numbers table. Next, we update the pre-populated NULL values of the `LN_Of_X` column with the natural logarithm values of the X column using the `UPDATE` statement. Lastly, we display the newly updated Numbers table using the `SELECT` statement.

The output is –

## Conclusion

Finding the natural logarithm of a number is one of the most important and widely used mathematical operations. I would encourage you to try the various use cases of `LN()` in MySQL for practice.