How to format uuid string from binary column in MySQL/MariaDB - mysql

Question

In MySQL/MariaDB the most efficient way to store uuid is in a BINARY(16) column. However, sometimes you want to obtain it as a formatted uuid string.
Given the following table structure, how would I obtain all uuids in a default formatted way?
CREATE TABLE foo (uuid BINARY(16));

Answer 1

The following would create the result I was after:
SELECT
LOWER(CONCAT(
SUBSTR(HEX(uuid), 1, 8), '-',
SUBSTR(HEX(uuid), 9, 4), '-',
SUBSTR(HEX(uuid), 13, 4), '-',
SUBSTR(HEX(uuid), 17, 4), '-',
SUBSTR(HEX(uuid), 21)
))
FROM foo;

Answer 2

MySQL 8 adds two new UUID functions:
UUID_TO_BIN
BIN_TO_UUID - this is the one you're looking for
So:
SELECT BIN_TO_UUID(uuid) FROM foo

Answer 3

In earlier (prior to 8) versions you can create a function in MySQL like the following:
CREATE
FUNCTION uuid_of(uuid BINARY(16))
RETURNS VARCHAR(36)
RETURN LOWER(CONCAT(
SUBSTR(HEX(uuid), 1, 8), '-',
SUBSTR(HEX(uuid), 9, 4), '-',
SUBSTR(HEX(uuid), 13, 4), '-',
SUBSTR(HEX(uuid), 17, 4), '-',
SUBSTR(HEX(uuid), 21)
));
And then simply use it in your queries:
SELECT
uuid_of(id)
name,
age
FROM users
And it produces:
(c6f5703b-fec2-43fd-8f45-45f06583d450, Some name, 20)

Answer 4

If you are looking for the opposite, i.e., how to convert from string to binary, perhaps to do a join or something, this is covered here : Convert UUID to/from binary in Node
This piece of SQL run on Mysql 5.7 helped lock in the concept for me:
SELECT
LOWER(CONCAT(
SUBSTR(HEX(UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', ''))), 1, 8), '-',
SUBSTR(HEX(UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', ''))), 9, 4), '-',
SUBSTR(HEX(UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', ''))), 13, 4), '-',
SUBSTR(HEX(UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', ''))), 17, 4), '-',
SUBSTR(HEX(UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', ''))), 21)
))
The output is 43d597d7-2323-325a-90fc-21fa5947b9f3.
string -> binary
So UNHEX(REPLACE('43d597d7-2323-325a-90fc-21fa5947b9f3', '-', '')) to convert a UUID to binary during an INSERT / UPDATE / JOIN / SELECT whatever, and
binary -> string
LOWER(CONCAT(
SUBSTR(HEX(uuid), 1, 8), '-',
SUBSTR(HEX(uuid), 9, 4), '-',
SUBSTR(HEX(uuid), 13, 4), '-',
SUBSTR(HEX(uuid), 17, 4), '-',
SUBSTR(HEX(uuid), 21)
))

Answer 5

The correct result is generated by the script below, the other scrips generated a UUID however not the right one.
CONCAT(
substr(hex(Id), 7, 2), substr(hex(Id), 5, 2), substr(hex(Id), 3, 2), substr(hex(Id), 1, 2), '-'
, substr(hex(Id), 11, 2) , substr(hex(Id), 9, 2) , '-'
, substr(hex(Id), 15, 2) , substr(hex(Id), 13, 2) , '-'
, substr(hex(Id), 17, 4) , '-'
, substr(hex(Id), 21, 12)
)
Results running the other scripts generated wrong UUID as per below:
Expected UUID - 2e9660c2-1e51-4b9e-9a86-6db1a2770422
What was generated - c260962e-511e-9e4b-9a86-6db1a2770422
As you can see they are different.

Answer 6

Here's an alternative using concat_ws
Store raw uuid in a variable #x
SELECT #x := hex(uuid)
FROM foo;
Use CONCAT_WS and SUBSTR to parse human readable UUID
SELECT
LOWER(CONCAT_WS('-',
SUBSTR(#x, 1, 8),
SUBSTR(#x, 9, 4),
SUBSTR(#x, 13, 4),
SUBSTR(#x, 17, 4),
SUBSTR(#x, 21)
)) AS uuid;

Answer 7

According to this Jira ticket https://jira.mariadb.org/browse/MDEV-15854 UUID_TO_BIN and BIN_TO_UUID did not make into the Mariadb Server release 10.5. If you are using this version and under of Mariadb Server you will have to use a custom implementation mentioned above.