{"id":40728,"date":"2024-11-21T04:48:06","date_gmt":"2024-11-20T18:48:06","guid":{"rendered":"https:\/\/database.guide\/?p=40728"},"modified":"2024-11-21T04:48:06","modified_gmt":"2024-11-20T18:48:06","slug":"understanding-the-log2-function-in-sqlite","status":"publish","type":"post","link":"https:\/\/database.guide\/understanding-the-log2-function-in-sqlite\/","title":{"rendered":"Understanding the LOG2() Function in SQLite"},"content":{"rendered":"\n

The log2()<\/code> function in SQLite calculates the base-2 logarithm of a given number. <\/p>\n\n\n\n

This function can be useful for scenarios such as binary calculations, information theory, or situations where the base-2 logarithm is needed.<\/p>\n\n\n\n\n\n\n\n

Syntax<\/h2>\n\n\n\n
log2(X)<\/code><\/pre>\n\n\n\n
Where X<\/em><\/code> is the number for which you want to calculate the base-2 logarithm. It must be a positive number greater than 0.<\/p>\n\n\n\n
Example<\/h2>\n\n\n\n
Let’s calculate the base-2 logarithm of 16<\/code>:<\/p>\n\n\n\n
SELECT log2(16);<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
+----------+
| log2(16) |
+----------+
| 4.0      |
+----------+<\/pre>\n\n\n\n
Explanation: The base-2 logarithm of 16 is 4 because 2 raised to the power of 4 = 16.<\/p>\n\n\n\n
Example with ROUND()<\/code><\/h2>\n\n\n\n
If you want to round the result, you can use the ROUND()<\/a><\/code> function in combination with log2()<\/code>. <\/p>\n\n\n\n
For example, to calculate the base-2 logarithm of 50<\/code> and round the result to 2 decimal places:<\/p>\n\n\n\n
SELECT log2(50) AS unrounded,\n       ROUND(log2(50), 2) AS rounded;<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
+------------------+---------+
|    unrounded     | rounded |
+------------------+---------+
| 5.64385618977472 | 5.64    |
+------------------+---------+<\/pre>\n\n\n\n
Explanation: The base-2 logarithm of 50 is approximately 5.64385618977472, and after rounding to two decimal places, the result is 5.64.<\/p>\n\n\n\n
We Must Pass a Positive Number<\/h2>\n\n\n\n
The argument X<\/em><\/code> must be a positive real number; passing zero or a negative number will result in NULL<\/code>.<\/p>\n\n\n\n
To demonstrate this, let’s first set a string for null values:<\/p>\n\n\n\n
.nullvalue 'null'<\/code><\/pre>\n\n\n\n
I did that because by default null values are returned as an empty string. I set .nullvalue<\/code> to null<\/code> in order to explicitly show when a null value is returned.<\/p>\n\n\n\n
Anyway, let’s now run the following query: <\/p>\n\n\n\n
SELECT log2(-50),\n       log2(0);<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
+-----------+---------+
| log2(-50) | log2(0) |
+-----------+---------+
| null      | null    |
+-----------+---------+<\/pre>\n\n\n\n
As expected, we can see that null was returned in both cases.<\/p>\n\n\n\n
Passing the Wrong Argument Type<\/h2>\n\n\n\n
Passing the wrong argument type results in null being returned:<\/p>\n\n\n\n
SELECT log2('Ten');<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
+-------------+
| log2('Ten') |
+-------------+
| null        |
+-------------+<\/pre>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
The log2() function in SQLite calculates the base-2 logarithm of a given number. This function can be useful for scenarios such as binary calculations, information theory, or situations where the base-2 logarithm is needed.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[100],"tags":[93,70,20],"class_list":["post-40728","post","type-post","status-publish","format-standard","hentry","category-sqlite","tag-functions","tag-mathematical-functions","tag-what-is"],"_links":{"self":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/40728","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/comments?post=40728"}],"version-history":[{"count":3,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/40728\/revisions"}],"predecessor-version":[{"id":40742,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/40728\/revisions\/40742"}],"wp:attachment":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/media?parent=40728"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/categories?post=40728"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/tags?post=40728"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}