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Chapter 8 code updates

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anthonydb 2020-09-15 22:30:43 -04:00
parent 9b8305ad6f
commit d2165e4f81
3 changed files with 181 additions and 63 deletions
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14
Chapter_07/Chapter_07.sql
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@ -117,6 +117,7 @@ ON district_2020.id = district_2035.id
WHERE district_2020.id IS NULL;
-- Listing 7-10: Querying specific columns in a join
SELECT district_2020.id,
district_2020.school_2020,
district_2035.school_2035
@ -124,6 +125,7 @@ FROM district_2020 LEFT JOIN district_2035
ON district_2020.id = district_2035.id;
-- Listing 7-11: Simplifying code with table aliases
SELECT d20.id,
d20.school_2020,
d35.school_2035
@ -131,6 +133,7 @@ FROM district_2020 AS d20 LEFT JOIN district_2035 AS d35
ON d20.id = d35.id;
-- Listing 7-12: Joining multiple tables
CREATE TABLE district_2020_enrollment (
id integer,
enrollment integer
@ -165,18 +168,21 @@ LEFT JOIN district_2020_grades AS gr
ON d20.id = gr.id;
-- Listing 7-13: Combining query results with UNION
SELECT * FROM district_2020
UNION
SELECT * FROM district_2035
ORDER BY id;
-- Listing 7-14: Combining query results with UNION ALL
SELECT * FROM district_2020
UNION ALL
SELECT * FROM district_2035
ORDER BY id;
-- Listing 7-15: Customizing a UNION query
SELECT '2020' AS year,
school_2020 AS school
FROM district_2020
@ -189,6 +195,7 @@ FROM district_2035
ORDER BY school, year;
-- Listing 7-16: Combining query results with INTERSECT and EXCEPT
SELECT * FROM district_2020
INTERSECT
SELECT * FROM district_2035
@ -200,14 +207,15 @@ SELECT * FROM district_2035
ORDER BY id;
-- Listing 7-17: Performing math on joined Census population estimates tables
CREATE TABLE us_counties_pop_est_2010 (
state_fips text, -- State FIPS code
county_fips text, -- County FIPS code
region smallint, -- Region
state_name text, -- State name
state_name text, -- State name
county_name text, -- County name
estimates_base_2010 integer, -- 4/1/2010 resident total population estimates base
CONSTRAINT counties_2010_key PRIMARY KEY (state_fips, county_fips)
CONSTRAINT counties_2010_key PRIMARY KEY (state_fips, county_fips)
);
COPY us_counties_pop_est_2010
@ -220,7 +228,7 @@ SELECT c2019.county_name,
c2010.estimates_base_2010 AS pop_2010,
c2019.pop_est_2019 - c2010.estimates_base_2010 AS raw_change,
round( (c2019.pop_est_2019::numeric - c2010.estimates_base_2010)
/ c2010.estimates_base_2010 * 100, 1 ) AS pct_change
/ c2010.estimates_base_2010 * 100, 1 ) AS pct_change
FROM us_counties_pop_est_2019 AS c2019
JOIN us_counties_pop_est_2010 AS c2010
ON c2019.state_fips = c2010.state_fips

135
Chapter_08/Chapter_08.sql
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@ -1,20 +1,20 @@
-- FIRST EDITION FILE; IGNORE
--------------------------------------------------------------
-- Practical SQL: A Beginner's Guide to Storytelling with Data
---------------------------------------------------------------------------
-- 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 varchar(10) CONSTRAINT license_key PRIMARY KEY,
first_name varchar(50),
last_name varchar(50)
license_id text CONSTRAINT license_key PRIMARY KEY,
first_name text,
last_name text
);
-- Drop the table before trying again
@ -22,88 +22,102 @@ 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),
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
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');
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 varchar(10),
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, '1/22/2022', 'Y');
INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/22/2017', 'Y');
VALUES(775, '1/23/2022', 'Y');
INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/23/2017', 'Y');
VALUES(775, '1/23/2022', 'N');
INSERT INTO natural_key_composite_example (student_id, school_day, present)
VALUES(775, '1/23/2017', 'N');
-- Listing 8-5: Declaring a bigserial column as a surrogate key
-- Listing 8-5: Declaring a bigint column as a surrogate key using IDENTITY
CREATE TABLE surrogate_key_example (
order_number bigserial,
product_name varchar(50),
order_date date,
CONSTRAINT order_key PRIMARY KEY (order_number)
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_date)
VALUES ('Beachball Polish', '2015-03-17'),
('Wrinkle De-Atomizer', '2017-05-22'),
('Flux Capacitor', '1985-10-26');
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: A foreign key example
-- Listing 8-6:
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 varchar(10),
first_name varchar(50),
last_name varchar(50),
license_id text,
first_name text,
last_name text,
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),
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', 'Lynn', 'Malero');
VALUES ('T229901', 'Steve', 'Rothery');
INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A203391', '3/17/2017', 'T229901');
VALUES ('A203391', '3/17/2022', 'T229901');
INSERT INTO registrations (registration_id, registration_date, license_id)
VALUES ('A75772', '3/17/2017', 'T000001');
VALUES ('A75772', '3/17/2022', 'T000001');
-- Listing 8-7: CHECK constraint examples
-- Listing 8-8: CHECK constraint examples
CREATE TABLE check_constraint_example (
user_id bigserial,
user_role varchar(50),
salary integer,
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_zero CHECK (salary > 0)
CONSTRAINT check_salary_not_below_zero CHECK (salary >= 0)
);
-- Both of these will fail:
@ -111,15 +125,16 @@ INSERT INTO check_constraint_example (user_role)
VALUES ('admin');
INSERT INTO check_constraint_example (salary)
VALUES (0);
VALUES (-10000);
-- Listing 8-8: UNIQUE constraint example
-- Listing 8-9: 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),
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)
);
@ -132,16 +147,16 @@ VALUES ('Betty', 'Diaz', 'bdiaz@example.org');
INSERT INTO unique_constraint_example (first_name, last_name, email)
VALUES ('Sasha', 'Lee', 'slee@example.org');
-- Listing 8-9: NOT NULL constraint example
-- Listing 8-10: NOT NULL constraint example
CREATE TABLE not_null_example (
student_id bigserial,
first_name varchar(50) NOT NULL,
last_name varchar(50) NOT NULL,
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 8-10: Dropping and adding a primary key and a NOT NULL constraint
-- 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;
@ -155,15 +170,15 @@ 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 8-11: Importing New York City address data
-- Listing 8-12: 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),
street_number text,
street text,
unit text,
postcode text,
id integer CONSTRAINT new_york_key PRIMARY KEY
);
@ -171,7 +186,7 @@ COPY new_york_addresses
FROM 'C:\YourDirectory\city_of_new_york.csv'
WITH (FORMAT CSV, HEADER);
-- Listing 8-12: Benchmark queries for index performance
-- Listing 8-13: Benchmark queries for index performance
EXPLAIN ANALYZE SELECT * FROM new_york_addresses
WHERE street = 'BROADWAY';
@ -182,6 +197,6 @@ WHERE street = '52 STREET';
EXPLAIN ANALYZE SELECT * FROM new_york_addresses
WHERE street = 'ZWICKY AVENUE';
-- Listing 8-13: Creating a B-Tree index on the new_york_addresses table
-- Listing 8-14: Creating a B-Tree index on the new_york_addresses table
CREATE INDEX street_idx ON new_york_addresses (street);

95
Try_It_Yourself/Try_It_Yourself.sql
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@ -374,6 +374,101 @@ FROM us_counties_pop_est_2019 AS c2019
JOIN us_counties_pop_est_2010 AS c2010
ON c2019.state_fips = c2010.state_fips
AND c2019.county_fips = c2010.county_fips;
----------------------------------------------------------------------------
-- Chapter 8: Table Design That Works for You
----------------------------------------------------------------------------
-- Consider the following two tables from a database you’re making to keep
-- track of your vinyl LP collection. Start by reviewing these CREATE TABLE
-- statements.
-- The albums table includes information specific to the overall collection
-- of songs on the disc. The songs table catalogs each track on the album.
-- Each song has a title and a column for its composers, who might be
-- different than the album artist.
CREATE TABLE albums (
album_id bigserial,
catalog_code varchar(100),
title text,
artist text,
release_date date,
genre varchar(40),
description text
);
CREATE TABLE songs (
song_id bigserial,
title text,
composers text,
album_id bigint
);
-- Use the tables to answer these questions:
-- 1. Modify these CREATE TABLE statements to include primary and foreign keys
-- plus additional constraints on both tables. Explain why you made your
-- choices.
-- Answer (yours may vary slightly):
CREATE TABLE albums (
album_id bigint GENERATED ALWAYS AS IDENTITY,
catalog_code text NOT NULL,
title text NOT NULL,
artist text NOT NULL,
release_date date,
genre text,
description text,
CONSTRAINT album_id_key PRIMARY KEY (album_id),
CONSTRAINT release_date_check CHECK (release_date > '1/1/1925')
);
CREATE TABLE songs (
song_id bigint GENERATED ALWAYS AS IDENTITY,
title text NOT NULL,
composer text NOT NULL,
album_id bigint REFERENCES albums (album_id),
CONSTRAINT song_id_key PRIMARY KEY (song_id)
);
-- Answers:
-- a) Both tables get a primary key using surrogate key id values that are
-- auto-generated via IDENTITY.
-- b) The songs table references albums via a foreign key constraint.
-- c) In both tables, the title and artist/composer columns cannot be empty, which
-- is specified via a NOT NULL constraint. We assume that every album and
-- song should at minimum have that information.
-- d) In albums, the release_date column has a CHECK constraint
-- because it would be likely impossible for us to own an LP made before 1925.
-- 2. Instead of using album_id as a surrogate key for your primary key, are
-- there any columns in albums that could be useful as a natural key? What would
-- you have to know to decide?
-- Answer:
-- We could consider the catalog_code. We would have to answer yes to
-- these questions:
-- 1. Is it going to be unique across all albums released by all companies?
-- 2. Will an album always have a catelog code?
-- 3. To speed up queries, which columns are good candidates for indexes?
-- Answer:
-- Primary key columns get indexes by default, but we should add an index
-- to the album_id foreign key column in the songs table because we'll use
-- it in table joins. It's likely that we'll query these tables to search
-- by titles and artists, so those columns in both tables should get indexes
-- too. The release_date in albums also is a candidate if we expect
-- to perform many queries that include date ranges.