DevTut

# Table Creation

# Table creation with Primary Key

CREATE TABLE person (
    person_id BIGINT NOT NULL,
    last_name VARCHAR(255) NOT NULL,
    first_name VARCHAR(255),
    address VARCHAR(255),
    city VARCHAR(255),
    PRIMARY KEY (person_id)
);

Alternatively, you can place the PRIMARY KEY constraint directly in the column definition:

CREATE TABLE person (
    person_id BIGINT NOT NULL PRIMARY KEY,
    last_name VARCHAR(255) NOT NULL,
    first_name VARCHAR(255),
    address VARCHAR(255),
    city VARCHAR(255)
);

It is recommended that you use lower case names for the table and as well as all the columns. If you use upper case names such as Person you would have to wrap that name in double quotes ("Person") in each and every query because PostgreSQL enforces case folding.

# Show table definition

Open the psql command line tool connected to the database where your table is. Then type the following command:

\d tablename

To get extended information type

\d+ tablename

If you have forgotten the name of the table, just type \d into psql to obtain a list of tables and views in the current database.

# Create table from select

Let's say you have a table called person:

CREATE TABLE person (
    person_id BIGINT NOT NULL,
    last_name VARCHAR(255) NOT NULL,
    first_name VARCHAR(255),
    age INT NOT NULL,
    PRIMARY KEY (person_id)
);

You can create a new table of people over 30 like this:

CREATE TABLE people_over_30 AS SELECT * FROM person WHERE age > 30;

# Create unlogged table

You can create unlogged tables so that you can make the tables considerably faster. Unlogged table skips writing write-ahead log which means it's not crash-safe and unable to replicate.

CREATE UNLOGGED TABLE person (
    person_id BIGINT NOT NULL PRIMARY KEY,
    last_name VARCHAR(255) NOT NULL,
    first_name VARCHAR(255),
    address VARCHAR(255),
    city VARCHAR(255)
);

# Create a table that references other table.

In this example, User Table will have a column that references the Agency table.

CREATE TABLE agencies ( -- first create the agency table
  id SERIAL PRIMARY KEY,
  name TEXT NOT NULL
)

CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  agency_id NOT NULL INTEGER REFERENCES agencies(id) DEFERRABLE INITIALLY DEFERRED -- this is going to references your agency table.
)

← SELECT →