postgres alter table code example

Example 1: postgresql add column with constraint

ALTER TABLE customers 
ADD COLUMN contact_name VARCHAR NOT NULL;

Example 2: postgresql change default value

ALTER TABLE ONLY users ALTER COLUMN lang SET DEFAULT 'en_GB';

Example 3: alter column in table postgres

ALTER TABLE table_name
  ALTER COLUMN column_name TYPE column_definition;

Example 4: postgres how to add field created at

CREATE TABLE my_table
(
	id serial NOT NULL,
    user_name text,
	created_at timestamp with time zone DEFAULT CURRENT_TIMESTAMP //here
)

Example 5: alter table add column postgres

Alter Postgres Table