How the UNCOMPRESS() function works in Mariadb?

The UNCOMPRESS() function in MariaDB is used to uncompress a string that has been compressed using the COMPRESS() function. It takes a compressed string as input and returns the original uncompressed string.

Syntax

The syntax for the MariaDB UNCOMPRESS() function is as follows:

UNCOMPRESS(compressed_string)

• compressed_string: The input string that has been compressed using the COMPRESS() function.

The function returns the original uncompressed string. If the input is not a compressed string, it returns NULL.

Examples

Example 1: Uncompressing a Simple String

This example demonstrates how to uncompress a string that has been compressed using the COMPRESS() function.

SELECT UNCOMPRESS(COMPRESS('Hello, World!')) AS uncompressed_string;

Output:

+---------------------+
| uncompressed_string |
+---------------------+
| Hello, World!       |
+---------------------+

The UNCOMPRESS() function successfully uncompressed the compressed string ‘Hello, World!’.

Example 2: Uncompressing a String from a Table Column

This example shows how to use the UNCOMPRESS() function to uncompress a compressed string column in a table.

DROP TABLE IF EXISTS example;
CREATE TABLE example (data BLOB);
INSERT INTO example VALUES (COMPRESS('This is a compressed string.'));

SELECT UNCOMPRESS(data) AS uncompressed_data FROM example;

Output:

+------------------------------+
| uncompressed_data            |
+------------------------------+
| This is a compressed string. |
+------------------------------+

The UNCOMPRESS() function uncompressed the compressed data stored in the data column of the example table.

Example 3: Uncompressing a Longer String

This example demonstrates how the UNCOMPRESS() function handles uncompressing a longer string.

SET @original_string = REPEAT('Lorem ipsum dolor sit amet, ', 100);
SET @compressed_string = COMPRESS(@original_string);

SELECT LENGTH(@original_string) AS original_length,
       LENGTH(@compressed_string) AS compressed_length,
       LENGTH(UNCOMPRESS(@compressed_string)) AS uncompressed_length;

Output:

+-----------------+-------------------+---------------------+
| original_length | compressed_length | uncompressed_length |
+-----------------+-------------------+---------------------+
|            2800 |                63 |                2800 |
+-----------------+-------------------+---------------------+

In this example, a long string is compressed using the COMPRESS() function, and then the UNCOMPRESS() function is used to uncompress it. The output shows the length of the original string, the compressed string, and the uncompressed string, demonstrating that the UNCOMPRESS() function correctly restored the original string.

Example 4: Handling an Uncompressed String

This example shows the behavior of the UNCOMPRESS() function when provided with an uncompressed string.

SELECT UNCOMPRESS('Hello, World!') AS uncompressed_string;

Output:

+---------------------+
| uncompressed_string |
+---------------------+
| NULL                |
+---------------------+

When an uncompressed string is provided as input to the UNCOMPRESS() function, it returns NULL because the input is not a valid compressed string.

Example 5: Combining UNCOMPRESS() with Other Functions

This example demonstrates how to combine the UNCOMPRESS() function with other string functions.

SELECT CONCAT('Uncompressed string: ', UNCOMPRESS(COMPRESS('Hello, World!'))) AS result;

Output:

+------------------------------------+
| result                             |
+------------------------------------+
| Uncompressed string: Hello, World! |
+------------------------------------+

In this example, the CONCAT() function is used to concatenate a prefix string with the uncompressed string obtained by applying the UNCOMPRESS() function to a compressed string.

Related Functions

The following are some functions related to the MariaDB UNCOMPRESS() function:

• MariaDB COMPRESS() function is used to compress a string into a binary string.
• MariaDB ENCODE() function is used to encode a string using a specific encoding method.
• MariaDB DECODE() function is used to decode a string that has been encoded using a specific encoding method.

Conclusion

The UNCOMPRESS() function in MariaDB is a useful tool for decompressing strings that have been compressed using the COMPRESS() function. By understanding the syntax and usage examples, you can effectively incorporate this function into your SQL queries and data manipulation tasks. Whether you need to store compressed data in your database or transmit compressed data over the network, the UNCOMPRESS() function provides a convenient way to retrieve the original uncompressed data when needed.