On 2013-09-27 14:27, mdr wrote:
I had a question on creating PK with alter table, after table is created.
I understand I create a PK id during create table by stating id as follows:
id serial primary key
It implicitly creates index and the sequence testing_id_seq to be associated
with the id field.
I can list the sequence with \ds.
...
However if I create a primary key with alter table primary key as in:
import_dbms_db=> alter table testing ADD CONSTRAINT pkid PRIMARY KEY (id);
NOTICE: ALTER TABLE / ADD PRIMARY KEY will create implicit index "pkid" for
table "testing"
ALTER TABLE
import_dbms_db=> \ds
No relations found.
It does not create a sequence.
Correct - it is the type of the column ("serial") in your create table
statement that automatically creates the sequence and attaches it to the
column, not the primary key constraint.
Also during creating indexes (primary, secondary or foreign) am I allowed to
create indexes with same name but on different tables? Or do index names
have to be different across tables? probably good programming practice as
well to have different index names across tables even if allowed?
Yes, index names must be unique within a schema. I usually name indexes
something like "idx_<tablename>_<indexed column(s) name(s)>" to
differentiate everything.
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