260 lines
6.7 KiB
SQL
260 lines
6.7 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 10 Code Examples
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----------------------------------------------------------------------------
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-- Listing 10-1: Importing the FSIS Meat, Poultry, and Egg Inspection Directory
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-- https://catalog.data.gov/dataset/fsis-meat-poultry-and-egg-inspection-directory-by-establishment-name
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CREATE TABLE meat_poultry_egg_inspect (
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est_number text CONSTRAINT est_number_key PRIMARY KEY,
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company text,
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street text,
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city text,
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st text,
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zip text,
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phone text,
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grant_date date,
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activities text,
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dbas text
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);
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COPY meat_poultry_egg_inspect
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FROM 'C:\YourDirectory\MPI_Directory_by_Establishment_Name.csv'
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WITH (FORMAT CSV, HEADER, DELIMITER ',');
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CREATE INDEX company_idx ON meat_poultry_egg_inspect (company);
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-- Count the rows imported:
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SELECT count(*) FROM meat_poultry_egg_inspect;
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-- Listing 10-2: Finding multiple companies at the same address
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SELECT company,
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street,
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city,
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st,
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count(*) AS address_count
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FROM meat_poultry_egg_inspect
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GROUP BY company, street, city, st
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HAVING count(*) > 1
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ORDER BY company, street, city, st;
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-- Listing 10-3: Grouping and counting states
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SELECT st,
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count(*) AS st_count
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FROM meat_poultry_egg_inspect
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GROUP BY st
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ORDER BY st;
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-- Listing 10-4: Using IS NULL to find missing values in the st column
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SELECT est_number,
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company,
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city,
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st,
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zip
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FROM meat_poultry_egg_inspect
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WHERE st IS NULL;
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-- Listing 10-5: Using GROUP BY and count() to find inconsistent company names
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SELECT company,
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count(*) AS company_count
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FROM meat_poultry_egg_inspect
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GROUP BY company
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ORDER BY company ASC;
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-- Listing 10-6: Using length() and count() to test the zip column
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SELECT length(zip),
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count(*) AS length_count
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FROM meat_poultry_egg_inspect
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GROUP BY length(zip)
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ORDER BY length(zip) ASC;
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-- Listing 10-7: Filtering with length() to find short zip values
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SELECT st,
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count(*) AS st_count
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FROM meat_poultry_egg_inspect
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WHERE length(zip) < 5
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GROUP BY st
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ORDER BY st ASC;
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-- Listing 10-8: Backing up a table
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CREATE TABLE meat_poultry_egg_inspect_backup AS
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SELECT * FROM meat_poultry_egg_inspect;
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-- Check number of records:
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SELECT
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(SELECT count(*) FROM meat_poultry_egg_inspect) AS original,
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(SELECT count(*) FROM meat_poultry_egg_inspect_backup) AS backup;
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-- Listing 10-9: Creating and filling the st_copy column with ALTER TABLE and UPDATE
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ALTER TABLE meat_poultry_egg_inspect ADD COLUMN st_copy varchar(2);
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UPDATE meat_poultry_egg_inspect
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SET st_copy = st;
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-- Listing 10-10: Checking values in the st and st_copy columns
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SELECT st,
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st_copy
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FROM meat_poultry_egg_inspect
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ORDER BY st;
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-- Listing 10-11: Updating the st column for three establishments
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UPDATE meat_poultry_egg_inspect
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SET st = 'MN'
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WHERE est_number = 'V18677A';
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UPDATE meat_poultry_egg_inspect
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SET st = 'AL'
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WHERE est_number = 'M45319+P45319';
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UPDATE meat_poultry_egg_inspect
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SET st = 'WI'
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WHERE est_number = 'M263A+P263A+V263A';
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-- Listing 10-12: Restoring original st column values
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-- Restoring from the column backup
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UPDATE meat_poultry_egg_inspect
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SET st = st_copy;
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-- Restoring from the table backup
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UPDATE meat_poultry_egg_inspect original
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SET st = backup.st
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FROM meat_poultry_egg_inspect_backup backup
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WHERE original.est_number = backup.est_number;
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-- Listing 10-13: Creating and filling the company_standard column
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ALTER TABLE meat_poultry_egg_inspect ADD COLUMN company_standard varchar(100);
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UPDATE meat_poultry_egg_inspect
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SET company_standard = company;
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-- Listing 10-14: Use UPDATE to modify field values that match a string
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UPDATE meat_poultry_egg_inspect
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SET company_standard = 'Armour-Eckrich Meats'
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WHERE company LIKE 'Armour%';
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SELECT company, company_standard
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FROM meat_poultry_egg_inspect
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WHERE company LIKE 'Armour%';
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-- Listing 10-15: Creating and filling the zip_copy column
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ALTER TABLE meat_poultry_egg_inspect ADD COLUMN zip_copy varchar(5);
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UPDATE meat_poultry_egg_inspect
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SET zip_copy = zip;
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-- Listing 10-16: Modify codes in the zip column missing two leading zeros
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UPDATE meat_poultry_egg_inspect
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SET zip = '00' || zip
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WHERE st IN('PR','VI') AND length(zip) = 3;
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-- Listing 10-17: Modify codes in the zip column missing one leading zero
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UPDATE meat_poultry_egg_inspect
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SET zip = '0' || zip
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WHERE st IN('CT','MA','ME','NH','NJ','RI','VT') AND length(zip) = 4;
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-- Listing 10-18: Creating and filling a state_regions table
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CREATE TABLE state_regions (
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st varchar(2) CONSTRAINT st_key PRIMARY KEY,
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region varchar(20) NOT NULL
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);
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COPY state_regions
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FROM 'C:\YourDirectory\state_regions.csv'
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WITH (FORMAT CSV, HEADER, DELIMITER ',');
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-- Listing 10-19: Adding and updating an inspection_date column
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ALTER TABLE meat_poultry_egg_inspect ADD COLUMN inspection_date date;
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UPDATE meat_poultry_egg_inspect inspect
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SET inspection_date = '20110-12-01'
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WHERE EXISTS (SELECT state_regions.region
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FROM state_regions
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WHERE inspect.st = state_regions.st
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AND state_regions.region = 'New England');
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-- Listing 10-20: Viewing updated inspection_date values
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SELECT st, inspection_date
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FROM meat_poultry_egg_inspect
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GROUP BY st, inspection_date
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ORDER BY st;
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-- Listing 10-21: Delete rows matching an expression
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DELETE FROM meat_poultry_egg_inspect
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WHERE st IN('PR','VI');
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-- Listing 10-22: Remove a column from a table using DROP
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ALTER TABLE meat_poultry_egg_inspect DROP COLUMN zip_copy;
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-- Listing 10-23: Remove a table from a database using DROP
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DROP TABLE meat_poultry_egg_inspect_backup;
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-- Listing 10-24: Demonstrating a transaction block
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-- Start transaction and perform update
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START TRANSACTION;
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UPDATE meat_poultry_egg_inspect
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SET company = 'AGRO Merchantss Oakland LLC'
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WHERE company = 'AGRO Merchants Oakland, LLC';
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-- view changes
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SELECT company
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FROM meat_poultry_egg_inspect
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WHERE company LIKE 'AGRO%'
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ORDER BY company;
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-- Revert changes
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ROLLBACK;
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-- See restored state
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SELECT company
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FROM meat_poultry_egg_inspect
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WHERE company LIKE 'AGRO%'
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ORDER BY company;
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-- Alternately, commit changes at the end:
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START TRANSACTION;
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UPDATE meat_poultry_egg_inspect
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SET company = 'AGRO Merchants Oakland LLC'
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WHERE company = 'AGRO Merchants Oakland, LLC';
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COMMIT;
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-- Listing 10-25: Backing up a table while adding and filling a new column
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CREATE TABLE meat_poultry_egg_inspect_backup AS
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SELECT *,
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'2018-02-07'::date AS reviewed_date
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FROM meat_poultry_egg_inspect;
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-- Listing 10-26: Swapping table names using ALTER TABLE
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ALTER TABLE meat_poultry_egg_inspect RENAME TO meat_poultry_egg_inspect_temp;
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ALTER TABLE meat_poultry_egg_inspect_backup RENAME TO meat_poultry_egg_inspect;
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ALTER TABLE meat_poultry_egg_inspect_temp RENAME TO meat_poultry_egg_inspect_backup;
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