How to change a PG column to NULLABLE TRUE?

问题

How can I accomplish this using Postgres? I've tried the code below but it doesn't work:

ALTER TABLE mytable ALTER COLUMN mycolumn BIGINT NULL; 

回答1:

From the fine manual:

ALTER TABLE mytable ALTER COLUMN mycolumn DROP NOT NULL;

There's no need to specify the type when you're just changing the nullability.

来源：https://stackoverflow.com/questions/4812933/how-to-change-a-pg-column-to-nullable-true