Postgres中的default和set default之间有什么区别？

Question

I am kind of new to Postgres and I'm trying to use the following query in Postgres:

alter table tablename add column col1 enum('r', 'g', 'b') not null set default 'r';

It is giving me an error. When I changed it to default instead of set default , it worked fine.

Just wondering what the reason might be!

Answer 1

As for "why does it work"?

I suspect that you were using it in one of the following two ways:

alter table tablename add column col1 text default 'r';

and

alter table tablename alter column col1 set default 'r';

Note that the former alters the table by adding a column with a default value, while in the latter, the column already exists and you alter the column by setting a default value.

You can find more information about defaults in create table and alter table