PostgreSQL provides a built-in **LOG()** function to calculate the logarithm of a number to the base ten or the specified base. It is a mathematical function that accepts a numeric value, double precision value, or a numeric expression and retrieves the base 10 logarithms of the given number/expression.

This blog post will demonstrate the working of the **LOG()** function via practical examples. So, let’s get started.

**How to Use LOG() Function in Postgres?**

By default, the LOG() function calculates the base 10 logarithms of a number. However, you can specify the base of your choice as an argument to the LOG() function.

**Syntax**

Use one of the following syntaxes to calculate the logarithms of a number using the LOG() function:

LOG(num);

Or

LOG(base, num);

Here, "num" can be numeric or double precision value. Or it can be a numeric expression.

**Example 1: Base 10 Logarithm**

Let’s pass a number to the LOG() function to calculate the base 10 log of the input number:

SELECT LOG(72);

The output shows that the LOG() function retrieves the base 10 logarithms of the “72”.

**Example 2: Base 2 Logarithm**

In this example, we will calculate the base 2 logarithm of a number:

SELECT LOG(2.0, 72);

The output shows that the LOG() function retrieves the base 2 logarithms of the input number.

**Example 3: Pass an Expression to the LOG() Function**

In this example, we will pass an expression to the LOG() function:

SELECT LOG(10 * 2);

The output authenticates the working of the LOG() function.

**Example 4: How to Use the LOG() Function on Table’s Data?**

Let’s create a sample table named exm_tab with two columns: exp_base and exp_num:

CREATE TABLE exm_tab( exp_base NUMERIC, exp_num NUMERIC );

Now we will insert some records into the newly created table:

INSERT INTO exm_tab(exp_base, exp_num) VALUES (10, 200.00), (2, 200.00), (10, 20), (10, 20);

To see the newly inserted data, execute the SELECT command as follows:

SELECT * FROM exm_tab;

Let’s utilize the LOG() function on the “exm_tab” table to calculate the logarithm of various numbers:

SELECT LOG(exp_base, exp_num) FROM exm_tab;

This is how you can utilize the LOG() function on the table’s data.

**Conclusion**

PostgreSQL provides a built-in mathematical function named **LOG()** that calculates the logarithm of a number to the base ten or the specified base. By default, the LOG() function calculates the base 10 logarithms of a number. However, you can specify the base of your choice as an argument to the LOG() function. This blog post considered numerous use cases of the LOG() function and practical examples.