practical-sql-2/Chapter_08/Chapter_08.sql

---------------------------------------------------------------------------
-- Practical SQL: A Beginner's Guide to Storytelling with Data, 2nd Edition
-- by Anthony DeBarros

-- Chapter 8 Code Examples
----------------------------------------------------------------------------

-- Listing 8-1: Declaring a single-column natural key as primary key

-- As a column constraint
CREATE TABLE natural_key_example (
    license_id text CONSTRAINT license_key PRIMARY KEY,
    first_name text,
    last_name text
);

-- Drop the table before trying again
DROP TABLE natural_key_example;

-- As a table constraint
CREATE TABLE natural_key_example (
    license_id text,
    first_name text,
    last_name text,
    CONSTRAINT license_key PRIMARY KEY (license_id)
);

-- Listing 8-2: Example of a primary key violation
-- Note: You will need to create the natural_key_example table
-- using either of the two statements in Listing 8-1.

INSERT INTO natural_key_example (license_id, first_name, last_name)
VALUES ('T229901', 'Gem', 'Godfrey');

INSERT INTO natural_key_example (license_id, first_name, last_name)
VALUES ('T229901', 'John', 'Mitchell');

-- Listing 8-3: Declaring a composite primary key as a natural key

CREATE TABLE natural_key_composite_example (
    student_id text,
    school_day date,
    present boolean,
    CONSTRAINT student_key PRIMARY KEY (student_id, school_day)
);

-- Listing 8-4: Example of a composite primary key violation
INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '2022-01-22', 'Y');

INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '2022-01-23', 'Y');

INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '2022-01-23', 'N');

-- Listing 8-5: Declaring a bigint column as a surrogate key using IDENTITY

CREATE TABLE surrogate_key_example (
    order_number bigint GENERATED ALWAYS AS IDENTITY,
    product_name text,
    order_time timestamp with time zone,
    CONSTRAINT order_number_key PRIMARY KEY (order_number)
);

INSERT INTO surrogate_key_example (product_name, order_time)
VALUES ('Beachball Polish', '2020-03-15 09:21-07'),
       ('Wrinkle De-Atomizer', '2017-05-22 14:00-07'),
       ('Flux Capacitor', '1985-10-26 01:18:00-07');

SELECT * FROM surrogate_key_example;

-- Listing 8-6: Restarting an IDENTITY sequence

INSERT INTO surrogate_key_example
OVERRIDING SYSTEM VALUE
VALUES (4, 'Chicken Coop', '2021-09-03 10:33-07');

ALTER TABLE surrogate_key_example ALTER COLUMN order_number RESTART WITH 5;

INSERT INTO surrogate_key_example (product_name, order_time)
VALUES ('Aloe Plant', '2020-03-15 10:09-07');

SELECT * FROM surrogate_key_example;

-- Listing 8-7: A foreign key example

CREATE TABLE licenses (
    license_id text,
    first_name text,
    last_name text,
    CONSTRAINT licenses_key PRIMARY KEY (license_id)
);

CREATE TABLE registrations (
    registration_id text,
    registration_date timestamp with time zone,
    license_id text REFERENCES licenses (license_id),
    CONSTRAINT registration_key PRIMARY KEY (registration_id, license_id)
);

INSERT INTO licenses (license_id, first_name, last_name)
VALUES ('T229901', 'Steve', 'Rothery');

INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A203391', '2022-03-17', 'T229901');

INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A75772', '2022-03-17', 'T000001');

-- Listing 8-8: Examples of CHECK constraints

CREATE TABLE check_constraint_example (
    user_id bigint GENERATED ALWAYS AS IDENTITY,
    user_role text,
    salary numeric(10,2),
    CONSTRAINT user_id_key PRIMARY KEY (user_id),
    CONSTRAINT check_role_in_list CHECK (user_role IN('Admin', 'Staff')),
    CONSTRAINT check_salary_not_below_zero CHECK (salary >= 0)
);

-- Both of these will fail:
INSERT INTO check_constraint_example (user_role)
VALUES ('admin');

INSERT INTO check_constraint_example (salary)
VALUES (-10000);

-- Listing 8-9: A UNIQUE constraint example

CREATE TABLE unique_constraint_example (
    contact_id bigint GENERATED ALWAYS AS IDENTITY,
    first_name text,
    last_name text,
    email text,
    CONSTRAINT contact_id_key PRIMARY KEY (contact_id),
    CONSTRAINT email_unique UNIQUE (email)
);

INSERT INTO unique_constraint_example (first_name, last_name, email)
VALUES ('Samantha', 'Lee', 'slee@example.org');

INSERT INTO unique_constraint_example (first_name, last_name, email)
VALUES ('Betty', 'Diaz', 'bdiaz@example.org');

INSERT INTO unique_constraint_example (first_name, last_name, email)
VALUES ('Sasha', 'Lee', 'slee@example.org');

-- Listing 8-10: A NOT NULL constraint example

CREATE TABLE not_null_example (
    student_id bigint GENERATED ALWAYS AS IDENTITY,
    first_name text NOT NULL,
    last_name text NOT NULL,
    CONSTRAINT student_id_key PRIMARY KEY (student_id)
);

-- Listing 8-11: Dropping and adding a primary key and a NOT NULL constraint

-- Drop
ALTER TABLE not_null_example DROP CONSTRAINT student_id_key;

-- Add
ALTER TABLE not_null_example ADD CONSTRAINT student_id_key PRIMARY KEY (student_id);

-- Drop
ALTER TABLE not_null_example ALTER COLUMN first_name DROP NOT NULL;

-- Add
ALTER TABLE not_null_example ALTER COLUMN first_name SET NOT NULL;

-- Listing 8-12: Importing New York City address data

CREATE TABLE new_york_addresses (
    longitude numeric(9,6),
    latitude numeric(9,6),
    street_number text,
    street text,
    unit text,
    postcode text,
    id integer CONSTRAINT new_york_key PRIMARY KEY
);

COPY new_york_addresses
FROM 'C:\YourDirectory\city_of_new_york.csv'
WITH (FORMAT CSV, HEADER);

-- Listing 8-13: Benchmark queries for index performance

EXPLAIN ANALYZE SELECT * FROM new_york_addresses
WHERE street = 'BROADWAY';

EXPLAIN ANALYZE SELECT * FROM new_york_addresses
WHERE street = '52 STREET';

EXPLAIN ANALYZE SELECT * FROM new_york_addresses
WHERE street = 'ZWICKY AVENUE';

-- Listing 8-14: Creating a B-tree index on the new_york_addresses table

CREATE INDEX street_idx ON new_york_addresses (street);