Chapter_07.sql

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

-- Chapter 7 Code Examples
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-- Listing 7-1: Declaring a single-column natural key as primary key

-- As a column constraint
CREATE TABLE natural_key_example (
    license_id varchar(10) CONSTRAINT license_key PRIMARY KEY,
    first_name varchar(50),
    last_name varchar(50)
);

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

-- As a table constraint
CREATE TABLE natural_key_example (
    license_id varchar(10),
    first_name varchar(50),
    last_name varchar(50),
    CONSTRAINT license_key PRIMARY KEY (license_id)
);

-- Listing 7-2: Example of a primary key violation
INSERT INTO natural_key_example (license_id, first_name, last_name)
VALUES ('T229901', 'Lynn', 'Malero');

INSERT INTO natural_key_example (license_id, first_name, last_name)
VALUES ('T229901', 'Sam', 'Tracy');

-- Listing 7-3: Declaring a composite primary key as a natural key
CREATE TABLE natural_key_composite_example (
    student_id varchar(10),
    school_day date,
    present boolean,
    CONSTRAINT student_key PRIMARY KEY (student_id, school_day)
);

-- Listing 7-4: Example of a composite primary key violation

INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/22/2017', 'Y');

INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/23/2017', 'Y');

INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/23/2017', 'N');

-- Listing 7-5: Declaring a bigserial column as a surrogate key

CREATE TABLE surrogate_key_example (
    order_number bigserial,
    product_name varchar(50),
    order_date date,
    CONSTRAINT order_key PRIMARY KEY (order_number)
);

INSERT INTO surrogate_key_example (product_name, order_date)
VALUES ('Beachball Polish', '2015-03-17'),
       ('Wrinkle De-Atomizer', '2017-05-22'),
       ('Flux Capacitor', '1985-10-26');

SELECT * FROM surrogate_key_example;

-- Listing 7-6: A foreign key example

CREATE TABLE licenses (
    license_id varchar(10),
    first_name varchar(50),
    last_name varchar(50),
    CONSTRAINT licenses_key PRIMARY KEY (license_id)
);

CREATE TABLE registrations (
    registration_id varchar(10),
    registration_date date,
    license_id varchar(10) REFERENCES licenses (license_id),
    CONSTRAINT registration_key PRIMARY KEY (registration_id, license_id)
);

INSERT INTO licenses (license_id, first_name, last_name)
VALUES ('T229901', 'Lynn', 'Malero');

INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A203391', '3/17/2017', 'T229901');

INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A75772', '3/17/2017', 'T000001');

-- Listing 7-7: CHECK constraint examples

CREATE TABLE check_constraint_example (
    user_id bigserial,
    user_role varchar(50),
    salary integer,
    CONSTRAINT user_id_key PRIMARY KEY (user_id),
    CONSTRAINT check_role_in_list CHECK (user_role IN('Admin', 'Staff')),
    CONSTRAINT check_salary_not_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 (0);

-- Listing 7-8: UNIQUE constraint example

CREATE TABLE unique_constraint_example (
    contact_id bigserial CONSTRAINT contact_id_key PRIMARY KEY,
    first_name varchar(50),
    last_name varchar(50),
    email varchar(200),
    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 7-9: NOT NULL constraint example

CREATE TABLE not_null_example (
    student_id bigserial,
    first_name varchar(50) NOT NULL,
    last_name varchar(50) NOT NULL,
    CONSTRAINT student_id_key PRIMARY KEY (student_id)
);

-- Listing 7-10: 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 7-11: Importing New York City address data

CREATE TABLE new_york_addresses (
    longitude numeric(9,6),
    latitude numeric(9,6),
    street_number varchar(10),
    street varchar(32),
    unit varchar(7),
    postcode varchar(5),
    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 7-12: 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 7-13: Creating a B-Tree index on the new_york_addresses table

CREATE INDEX street_idx ON new_york_addresses (street);