Postgres auto_increment

I was surprised that while creating a new table in postgres we don’t have a key word AUTO_INCREMENT in postgres. so how do we get it?

well, its simple, create a table with the column in which you want to add auto_increment, create a sequence, modify table just created to set default value to sequence, Thats it

create sequence error_number_seq;

create table error_patterns(

error_number INT PRIMARY KEY,

pattern VARCHAR(100)

);

alter table error_patterns alter column error_number set default nextval(‘error_number_seq’);

commit;

\d error_patterns

Table “public.error_patterns”

Column    |          Type          |                       Modifiers

————–+————————+——————————————————–

error_number | integer                | not null default nextval(‘error_number_seq’::regclass)

pattern      | character varying(100) |

Indexes:

“error_patterns_pkey” PRIMARY KEY, btree (error_number)

Database : Functional Dependency

definition :

A functional dependency occurs when one attribute uniquely determines the another attribute in a relation

written as A -> B, which is read as “B is functionally dependent on A”

Examples : SSN -> Name, means name is dependent on Social Security Number(SSN). while Name -> SSN doesn’t holds as there many be many names which are same but they do not correspond to same SSN(which is unique).

What are Superkeys ?

well, a set of attributes that contains a key is called “superkey”, or “superset of keys”