133 lines
4.7 KiB
SQL
133 lines
4.7 KiB
SQL
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-- Practical SQL: A Beginner's Guide to Storytelling with Data, 2nd Edition
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-- by Anthony DeBarros
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-- Chapter 5 Code Examples
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----------------------------------------------------------------------------
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-- Listing 5-1: Using COPY for data import
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-- This is example syntax only; running it will produce an error
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COPY table_name
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FROM 'C:\YourDirectory\your_file.csv'
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WITH (FORMAT CSV, HEADER);
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-- Listing 5-2: A CREATE TABLE statement for Census county population estimates
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-- Data dictionary for estimates available at: https://www2.census.gov/programs-surveys/popest/technical-documentation/file-layouts/2010-2019/co-est2019-alldata.pdf
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-- Data dictionary for additional columns at: http://www.census.gov/prod/cen2010/doc/pl94-171.pdf
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-- Note: Some columns have been given more descriptive names
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CREATE TABLE us_counties_pop_est_2019 (
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state_fips text, -- State FIPS code
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county_fips text, -- County FIPS code
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region smallint, -- Region
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state_name text, -- State name
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county_name text, -- County name
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area_land bigint, -- Area (Land) in square meters
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area_water bigint, -- Area (Water) in square meters
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internal_point_lat numeric(10,7), -- Internal point (latitude)
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internal_point_lon numeric(10,7), -- Internal point (longitude)
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pop_est_2018 integer, -- 2018-07-01 resident total population estimate
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pop_est_2019 integer, -- 2019-07-01 resident total population estimate
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births_2019 integer, -- Births from 2018-07-01 to 2019-06-30
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deaths_2019 integer, -- Deaths from 2018-07-01 to 2019-06-30
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international_migr_2019 integer, -- Net international migration from 2018-07-01 to 2019-06-30
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domestic_migr_2019 integer, -- Net domestic migration from 2018-07-01 to 2019-06-30
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residual_2019 integer, -- Residual for 2018-07-01 to 2019-06-30
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CONSTRAINT counties_2019_key PRIMARY KEY (state_fips, county_fips)
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);
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SELECT * FROM us_counties_pop_est_2019;
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-- Listing 5-3: Importing Census data using COPY
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-- Note! If you run into an import error here, be sure you downloaded the code and
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-- data for the book according to the steps listed in Chapter 1.
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-- Windows users: Please check the Note on PAGE XXXXXX as well.
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COPY us_counties_pop_est_2019
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FROM 'C:\YourDirectory\us_counties_pop_est_2019.csv'
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WITH (FORMAT CSV, HEADER);
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-- Checking the data
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SELECT * FROM us_counties_pop_est_2019;
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SELECT county_name, state_name, area_land
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FROM us_counties_pop_est_2019
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ORDER BY area_land DESC
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LIMIT 3;
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SELECT county_name, state_name, internal_point_lon
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FROM us_counties_pop_est_2019
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ORDER BY internal_point_lon DESC
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LIMIT 5;
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-- Listing 5-4: Creating a table to track supervisor salaries
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CREATE TABLE supervisor_salaries (
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id integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
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town text,
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county text,
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supervisor text,
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start_date text,
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salary numeric(10,2),
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benefits numeric(10,2)
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);
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-- Listing 5-5: Importing salaries data from CSV to three table columns
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COPY supervisor_salaries (town, supervisor, salary)
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FROM 'C:\YourDirectory\supervisor_salaries.csv'
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WITH (FORMAT CSV, HEADER);
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-- Check the data
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SELECT * FROM supervisor_salaries LIMIT 2;
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-- Listing 5-6 Use a temporary table to add a default value to a column during
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-- import
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DELETE FROM supervisor_salaries;
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CREATE TEMPORARY TABLE supervisor_salaries_temp
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(LIKE supervisor_salaries INCLUDING ALL);
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COPY supervisor_salaries_temp (town, supervisor, salary)
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FROM 'C:\YourDirectory\supervisor_salaries.csv'
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WITH (FORMAT CSV, HEADER);
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INSERT INTO supervisor_salaries (town, county, supervisor, salary)
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SELECT town, 'My County', supervisor, salary
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FROM supervisor_salaries_temp;
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DROP TABLE supervisor_salaries_temp;
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-- Check the data
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SELECT * FROM supervisor_salaries LIMIT 2;
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-- Listing 5-7: Export an entire table with COPY
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COPY us_counties_pop_est_2019
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TO 'C:\YourDirectory\us_counties_export.txt'
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WITH (FORMAT CSV, HEADER, DELIMITER '|');
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-- Listing 5-8: Exporting selected columns from a table with COPY
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COPY us_counties_pop_est_2019
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(county_name, internal_point_lat, internal_point_lon)
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TO 'C:\YourDirectory\us_counties_latlon_export.txt'
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WITH (FORMAT CSV, HEADER, DELIMITER '|');
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-- Listing 5-9: Exporting query results with COPY
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COPY (
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SELECT county_name, state_name
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FROM us_counties_pop_est_2019
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WHERE county_name ILIKE '%mill%'
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)
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TO 'C:\YourDirectory\us_counties_mill_export.csv'
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WITH (FORMAT CSV, HEADER);
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