postgresql alter table code example

Example 1: postgresql add column with constraint

ALTER TABLE customers 
ADD COLUMN contact_name VARCHAR NOT NULL;

Example 2: alter column in table postgres

ALTER TABLE table_name
  ALTER COLUMN column_name TYPE column_definition;

Example 3: postgres alter table add primary key

-- To set a column as primary key:
ALTER TABLE distributors ADD PRIMARY KEY (tablename);

Example 4: postgres create table

-- Basic table creation
CREATE TABLE table_name(
   column1 datatype,
   column2 datatype,
   column3 datatype,
   .....
   columnN datatype,
   PRIMARY KEY( one or more columns )
);

Example 5: postgresql insert column

ALTER TABLE table_name
ADD COLUMN new_column_name data_type constraint;

Example 6: 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
)