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SQL example creating table with auto-increment.

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There are four versions of UUIDs.

• UUID1 uses MAC address and timestamp to generate effective uniqueness.

• UUID3 and UUID 5 uses cryptographic hashing and application-provided text strings to generate UUID. (UUID 3 uses MD5 hashing, and UUID 5 uses SHA-1 hashing).

• UUID4 uses pseudo-random number generators to generate UUID.

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MySQL’s Replace Into Statement can help to make MySQL auto-increment work across multiple databases, set up a dedicated database with a single table and a single record whose sole purpose is to provide unique and incremental ID.

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CREATE TABLE ID (
id bigint(20) unsigned NOT NULL auto_increment,
stub char(1) NOT NULL default '',
PRIMARY KEY (id),
UNIQUE KEY stub (stub)
) ENGINE=MyISAM

When I need a new globally unique 64-bit ID I issue the following SQL.

REPLACE INTO ID (stub) VALUES ('a');
SELECT LAST_INSERT_ID();