# How to Use LOG() Function in PostgreSQL

> PostgreSQL provides a built-in mathematical function named LOG() that calculates the logarithm of a number to the base ten or the specified base.

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.

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