![]() ![]() This column will be calculated by a formula of the binary-form column: we convert the binary form back to hexadecimal digits and insert dashes. Perhaps the text form is still necessary in some application, so let’s keep it as an additional column in the table but, to minimize disk occupation, let’s make the text form a virtual generated column (that’s a new feature of MySQL 5.7, described in the documentation of CREATE TABLE). BINARY(16) is… well… just binary! No character set, no collation, just sixteen bytes. If the UUID has to be a primary key, the gain is even greater, as in InnoDB the primary key value is copied into all secondary index values. This binary form uses 16 bytes which is much smaller than VARCHAR(36) used by the human-readable form (which I’ll call the “text” form now). So we can use REPLACE() to remove dashes, and UNHEX() to transform eachĬreate table users(id_bin binary(16), name varchar(200)) insert into users values(unhex(replace(uuid(),’-‘,”)), ‘Andromeda’) each pair of characters is actually a hexadecimal number in the range 00-FF that makes 16 numbers in total (above: 0xAA, 0xB5, etc), each of them can be stored in a byte. ![]() So the first idea would be to simply do this: 12Ĭreate table users(id varchar(36), name varchar(200)) insert into users values(uuid(), ‘Andromeda’) īut this human-readable form of UUID isn’t compact let’s observe that: MySQL has a UUID() function, which makes MySQL generate a UUID value and return it in a human-readable form, of type VARCHAR(36). Say we have a table of users, and each user has a UUID. ![]() After successful execution of the above statement, it will generate the UUID value as follows: Different techniques The above function returns a UUID value in agreement with UUID version 1 described in RFC 4122. We can generate UUID values in MySQL using the function as follows: mysql> SELECT UUID() The following are the valid string format of the UUID values in MySQL which is an arrangement of 32 digit of the hexadecimal format along with four hyphens (-): a2720191-1cc6-11eb-9a2c-107d1a24f935 If the letter is not available, it will substitute the random number that does not guarantee the spatial uniqueness.
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