How add a Primary Key autoincremented on my existing table ?

Question

I have a table with some datas. Is there a way to add a PK without erase the table ?

Answer 1

Lets say you have a test1 table to which you want to add a id (surrogate) autoincremental PK:

   ALTER TABLE test1 ADD COLUMN id SERIAL;
   UPDATE test1 SET id = nextval(pg_get_serial_sequence('test1','id'));
   ALTER TABLE test1 ADD PRIMARY KEY (id);