MySQL set default id UUID

问题

I'm trying to create tables in a database that has an id field that will populate the id with an UUID by default.

I tried something like:

CREATE TABLE FOO (
  id CHAR(36) PRIMARY KEY DEFAULT uuid()
);

I greatly appreciate your assistance.

回答1:

MySQL as of 5.7 does not support using a function as the default value of a column.

The DEFAULT value clause in a data type specification indicates a default value for a column. With one exception, the default value must be a constant; it cannot be a function or an expression.

https://dev.mysql.com/doc/refman/5.7/en/data-type-defaults.html

The alternative would be to use a trigger to monitor the BEFORE INSERT of the desired table.

DELIMITER ;;
CREATE TRIGGER `foo_before_insert` 
BEFORE INSERT ON `foo` FOR EACH ROW 
BEGIN
  IF new.id IS NULL THEN
    SET new.id = uuid();
  END IF;
END;;
DELIMITER ;

This will change the default value of an INSERT statement to the uuid() value, unless it has been explicitly defined.

回答2:

If you use binary(16) as the type, you can set the default as follows:

unhex(replace(uuid(),'-',''))

来源：https://stackoverflow.com/questions/46134550/mysql-set-default-id-uuid