# Random Id (Continue...)

+ implement principle of AUTO_RANDOM
  + AUTO_RANDOM is an 8-byte bigint integer
  + Its highest bit is the sign bit
  + If you want to use random bits of different lengths, you can adjust the amount in parentheses after AUTO_RANDOM
```
CREATE TABLE t (a bigint PRIMARY KEY AUTO_RANDOM(3), b varchar(255))
```
------------------------------------------------------------
- Principle implement
  - AUTO_RANDOM is an 8-byte Bigint integer
  - Its highest bit is the sign bit
  - To use random bits of different lengths you can adjust the amount in parentheses after AUTO_RANDOM
CREATE TABLE t (a bigint PRIMARY KEY AUTO_RANDOM (3), b varchar (255))