11/23/2023 0 Comments Mysql uuid![]() ![]() A warning about replication before we start If you are using statement based replication between a master & slave (or master & master), the examples on this page will not replicate the UUID across to the slave server(s) and different UUID(s) will be created on the slave(s). See " Generating v4 UUIDs in MySQL" for a way to generate potentially more desirable UUIDs. This post shows how to set a column to a UUID/GUID by default in MySQL using a trigger. Example aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee Here, the first three numbers are generated from the low, middle, and high parts of a timestamp. | cf2dcd93-26b0-11eb-a894-0242ac110003 | Sergey Brin | In MySQL, a UUID value is a 128-bit number represented as a utf8 string, and the format in hexadecimal number will be as follows. If everything went well, at the end you should have output similar to: +-+-+ VALUES (uuid_to_bin(uuid()), 'Larry Page') Here's an example where a table users uses binary UUIDs for its primary key: CREATE TABLE users , 9, 0, '-'), 14, 0, '-'), 19, 0, '-'), 24, 0, '-') When working with MySQL it is common to choose auto incrementing integer primary keys however, there are situations where using a GUID/UUID is desirable. ![]() MySQL v8.0.0 (2016) added the function UUID_TO_BIN() which does the same thing: SELECT uuid_to_bin("f7c26694-aac6-4333-91c9-72c4441430e2") AS uuid_bin +-+Īnd it's easy to perform the reverse here: SELECT lower( insert( insert( insert( insert( A UUID is just a 128-bit value and it is usually represented in human-readable format as an UTF8 string composed of 5 groups of hexadecimal characters separated by dashes. Even better, comparison and sorting will use the numeric value of the column, which will perform much better than a string.Īll versions of MySQL can use UNHEX() and REPLACE() to do this: SELECT UNHEX(REPLACE("f7c26694-aac6-4333-91c9-72c4441430e2", "-", "")) AS unhex_replace +-+ The BINARY type isn't affected by the table character set (such as utf8mb4), it uses the binary character set and collation. If we strip the hyphens and convert the remaining 32 characters to BINARY, we can store UUIDs in only 16 bytes. UUIDs are supposed to be only 16 bytes, can't we do better? Binary UUID columns Universally unique identifiers (UUIDs) are 128-bit (16-byte) numbers that are designed to be globally unique, and as a result they make for great primary keys. Why You Should Use UUIDs for Your Primary Keys ![]()
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