Modifying Tables

Remember how our task table looks like right now:

create table task (
    id serial primary key,
    title text not null,
    description text not null,
    status status,
    duration integer check (duration > 0),
    created_at timestamp default current_timestamp not null
);

Adding and Dropping Columns

To add a column use the alter table ... add column statement:

alter table task add column priority text;

You could add constraints here:

alter table task add column priority text check (priority in ('low', 'medium', 'high'));

You can use the alter table ... drop column statement to remove a column:

alter table task
drop column priority;

Adding and Dropping Constraints

You can add a new constraint to a column using the alter table ... add constraint statement:

alter table task
add constraint check_duration_max check (duration <= 600);

You can drop an existing constraint to a column using the alter table ... drop constraint statement:

alter table task
drop constraint check_duration_max;

Renaming Columns and Tables

You can rename a column using the alter table ... rename column statement:

alter table task
rename column description to details;

You can rename an entire table using the alter table rename ... statement:

alter table task
rename to task_list;

Removing Tables

You can remove an entire table using the drop table statement:

drop table task;