MySQL MyISAM engine Change column default value optimization

If you need to change the default Value property of a column

Such as:

ALTER TABLE USER MODIFY COLUMN NAME VARCHAR (+) DEFAULT ' default_user ';

This causes the entire table to be locked, and all rows are updated before the lock resource is freed.

In this case, you can use this command

Alter TABLE USER ALTER COLUMN NAME SET DEFAULT ' Default_user ';

Instant completion. Because it changes only the. frm file.

MySQL MyISAM engine Change column default value optimization