How the LOG2() function works in Mariadb?

The LOG2() function is a mathematical function that returns the logarithm of a number to the base 2.

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The LOG2() function is a mathematical function that returns the logarithm of a number to the base 2. The logarithm to the base 2 is also known as the binary logarithm, as it represents the number of times a number can be divided by 2. The LOG2() function is useful for performing various calculations, such as binary search, bit manipulation, entropy, etc.

Syntax

The syntax of the LOG2() function is as follows:

LOG2(number)

The number argument is the number whose logarithm to the base 2 is to be returned. The number argument must be a positive value, otherwise the function returns NULL.

The LOG2() function returns a decimal value that represents the logarithm of the number to the base 2. If the number argument is NULL, the function returns NULL.

Examples

Example 1: Basic usage of the LOG2() function

The following example shows how to use the LOG2() function with a simple number. It returns the logarithm of the number 8 to the base 2.

SELECT LOG2(8);

The output is:

3

This means that the logarithm of 8 to the base 2 is 3, which means that 8 can be divided by 2 three times.

Example 2: Using the LOG2() function with a decimal number

The following example shows how to use the LOG2() function with a decimal number. It returns the logarithm of the number 2.5 to the base 2.

SELECT LOG2(2.5);

The output is:

1.321928094887362

This means that the logarithm of 2.5 to the base 2 is approximately 1.321928094887362.

Example 3: Using the LOG2() function with a negative number

The following example shows what happens when the LOG2() function is used with a negative number. It returns NULL, indicating that the logarithm to the base 2 is not defined for negative numbers.

SELECT LOG2(-5);

The output is:

NULL

This means that the logarithm of -5 to the base 2 is not defined.

There are some other functions that are related to the LOG2() function in Mariadb. They are:

  • LOG(): This function returns the natural logarithm of a number. The natural logarithm is the logarithm to the base e, where e is the mathematical constant that is approximately equal to 2.71828. The LOG() function can also accept an optional second argument that specifies a different base for the logarithm.
  • LOG10(): This function returns the logarithm of a number to the base 10. The logarithm to the base 10 is also known as the common logarithm, as it is widely used in mathematics and science.
  • POW(): This function returns the value of a number raised to the power of another number. It is the inverse of the LOG() function, meaning that POW(2, LOG2(x)) = x for any positive x.
  • BIT_COUNT(): This function returns the number of bits that are set to 1 in a binary representation of a number. It is related to the LOG2() function, as it can be used to calculate the minimum number of bits required to represent a number.

Here are some examples of using these related functions:

-- Get the natural logarithm of 10
SELECT LOG(10);

-- Get the logarithm of 100 to the base 10
SELECT LOG10(100);

-- Get the value of 2 raised to the power of 3
SELECT POW(2, 3);

-- Get the number of bits that are set to 1 in the binary representation of 13
SELECT BIT_COUNT(13);

Conclusion

In this article, we have learned how the LOG2() function works in Mariadb. We have seen its syntax, examples, and related functions. We have also learned how to use the LOG2() function to calculate the logarithm of a number to the base 2. The LOG2() function is a useful function to perform various calculations, such as binary search, bit manipulation, entropy, etc.