Posts Tagged ‘uuid’

MYSQL Creating several UUIDs at one single time

Wednesday, July 14th, 2010

I recently ran into the problem that I had too add two rows to a database that uses a UUID (in this case converted to a binary) as a key.
The problem I had was that running two insert statements after each other (just separated by “;”) then the same id was generated.
A workaround I have found is to sleep for a second between the two statements.

Examples (using SELECT instead of INSERT):
Getting the same id twice

SELECT UNHEX(REPLACE(UUID(),'-','')) AS uuid1,  UNHEX(REPLACE(UUID(),'-','')) AS uuid2;
-- Shows: "849392548f1311df91b70019dbd264f1"	"849392908f1311df91b70019dbd264f1"

Adding a sleep to get different ids

SELECT UNHEX(REPLACE(UUID(),'-','')) AS uuid1, SLEEP(1), UNHEX(REPLACE(UUID(),'-','')) AS uuid2
-- Shows: "3901c1928f1511df91b70019dbd264f1"	"0"	"399a5b148f1511df91b70019dbd264f1"

And another one using INSERTS

INSERT INTO testTable (id) VALUES (UNHEX(REPLACE(UUID(),'-','')));
SLEEP(1);
INSERT INTO testTable (id) VALUES (UNHEX(REPLACE(UUID(),'-','')));

Tags: ,
Posted in MySQL | No Comments »

PHP: converting a uuid stored as BINARY(16) in mysql to RFC 4122 format

Wednesday, June 16th, 2010

If you are storing uuid’s are BINARY(16) in the database, then the following will turn the stored id to the “original” format.

$uuidReadable = unpack("h*",$uuid);
$uuidReadable = preg_replace("/([0-9a-f]{8})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{12})/", "$1-$2-$3-$4-$5", $uuidReadable);
$uuidReadable = array_merge($uuidReadable);
echo "uuid is " . $uuidReadable[0];

Tags:
Posted in PHP5 | No Comments »

MySQL inserting UUID to a binary(16) field

Wednesday, June 16th, 2010

It is advantageous to store a UUID (acc to RFC 4122) in a binary(16) field in the database.
It is not hard to create such a table and to insert data into it.

CREATE TABLE IF NOT EXISTS test_table (
  id BINARY(16) NOT NULL,
  name varchar(128) NOT NULL,
  PRIMARY KEY  (id)
) 
 
INSERT INTO test_table (id, name) VALUES
(UNHEX(REPLACE(UUID(),'-','')), 'test1'),
(UNHEX(REPLACE(UUID(),'-','')), 'test2'),
(UNHEX(REPLACE(UUID(),'-','')), 'test3')

Tags:
Posted in MySQL | 1 Comment »