341 lines
9.6 KiB
SQL
341 lines
9.6 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 9 Code Examples
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----------------------------------------------------------------------------
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-- Listing 9-1: Creating and filling the 2018 Public Libraries Survey table
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CREATE TABLE pls_fy2018_libraries (
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stabr text NOT NULL,
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fscskey text CONSTRAINT fscskey_2018_pkey PRIMARY KEY,
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libid text NOT NULL,
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libname text NOT NULL,
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address text NOT NULL,
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city text NOT NULL,
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zip text NOT NULL,
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county text NOT NULL,
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phone text NOT NULL,
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c_relatn text NOT NULL,
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c_legbas text NOT NULL,
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c_admin text NOT NULL,
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c_fscs text NOT NULL,
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geocode text NOT NULL,
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lsabound text NOT NULL,
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startdate text NOT NULL,
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enddate text NOT NULL,
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popu_lsa integer NOT NULL,
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popu_und integer NOT NULL,
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centlib integer NOT NULL,
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branlib integer NOT NULL,
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bkmob integer NOT NULL,
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totstaff numeric(8,2) NOT NULL,
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bkvol integer NOT NULL,
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ebook integer NOT NULL,
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audio_ph integer NOT NULL,
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audio_dl integer NOT NULL,
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video_ph integer NOT NULL,
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video_dl integer NOT NULL,
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ec_lo_ot integer NOT NULL,
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subscrip integer NOT NULL,
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hrs_open integer NOT NULL,
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visits integer NOT NULL,
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reference integer NOT NULL,
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regbor integer NOT NULL,
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totcir integer NOT NULL,
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kidcircl integer NOT NULL,
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totpro integer NOT NULL,
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gpterms integer NOT NULL,
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pitusr integer NOT NULL,
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wifisess integer NOT NULL,
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obereg text NOT NULL,
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statstru text NOT NULL,
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statname text NOT NULL,
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stataddr text NOT NULL,
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longitude numeric(10,7) NOT NULL,
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latitude numeric(10,7) NOT NULL
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);
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COPY pls_fy2018_libraries
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FROM 'C:\YourDirectory\pls_fy2018_libraries.csv'
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WITH (FORMAT CSV, HEADER);
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CREATE INDEX libname_2018_idx ON pls_fy2018_libraries (libname);
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-- Listing 9-2: Creating and filling the 2017 and 2016 Public Libraries Survey tables
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CREATE TABLE pls_fy2017_libraries (
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stabr text NOT NULL,
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fscskey text CONSTRAINT fscskey_17_pkey PRIMARY KEY,
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libid text NOT NULL,
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libname text NOT NULL,
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address text NOT NULL,
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city text NOT NULL,
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zip text NOT NULL,
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county text NOT NULL,
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phone text NOT NULL,
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c_relatn text NOT NULL,
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c_legbas text NOT NULL,
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c_admin text NOT NULL,
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c_fscs text NOT NULL,
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geocode text NOT NULL,
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lsabound text NOT NULL,
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startdate text NOT NULL,
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enddate text NOT NULL,
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popu_lsa integer NOT NULL,
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popu_und integer NOT NULL,
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centlib integer NOT NULL,
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branlib integer NOT NULL,
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bkmob integer NOT NULL,
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totstaff numeric(8,2) NOT NULL,
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bkvol integer NOT NULL,
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ebook integer NOT NULL,
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audio_ph integer NOT NULL,
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audio_dl integer NOT NULL,
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video_ph integer NOT NULL,
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video_dl integer NOT NULL,
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ec_lo_ot integer NOT NULL,
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subscrip integer NOT NULL,
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hrs_open integer NOT NULL,
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visits integer NOT NULL,
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reference integer NOT NULL,
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regbor integer NOT NULL,
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totcir integer NOT NULL,
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kidcircl integer NOT NULL,
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totpro integer NOT NULL,
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gpterms integer NOT NULL,
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pitusr integer NOT NULL,
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wifisess integer NOT NULL,
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obereg text NOT NULL,
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statstru text NOT NULL,
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statname text NOT NULL,
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stataddr text NOT NULL,
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longitude numeric(10,7) NOT NULL,
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latitude numeric(10,7) NOT NULL
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);
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CREATE TABLE pls_fy2016_libraries (
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stabr text NOT NULL,
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fscskey text CONSTRAINT fscskey_16_pkey PRIMARY KEY,
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libid text NOT NULL,
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libname text NOT NULL,
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address text NOT NULL,
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city text NOT NULL,
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zip text NOT NULL,
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county text NOT NULL,
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phone text NOT NULL,
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c_relatn text NOT NULL,
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c_legbas text NOT NULL,
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c_admin text NOT NULL,
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c_fscs text NOT NULL,
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geocode text NOT NULL,
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lsabound text NOT NULL,
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startdate text NOT NULL,
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enddate text NOT NULL,
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popu_lsa integer NOT NULL,
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popu_und integer NOT NULL,
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centlib integer NOT NULL,
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branlib integer NOT NULL,
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bkmob integer NOT NULL,
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totstaff numeric(8,2) NOT NULL,
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bkvol integer NOT NULL,
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ebook integer NOT NULL,
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audio_ph integer NOT NULL,
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audio_dl integer NOT NULL,
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video_ph integer NOT NULL,
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video_dl integer NOT NULL,
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ec_lo_ot integer NOT NULL,
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subscrip integer NOT NULL,
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hrs_open integer NOT NULL,
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visits integer NOT NULL,
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reference integer NOT NULL,
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regbor integer NOT NULL,
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totcir integer NOT NULL,
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kidcircl integer NOT NULL,
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totpro integer NOT NULL,
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gpterms integer NOT NULL,
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pitusr integer NOT NULL,
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wifisess integer NOT NULL,
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obereg text NOT NULL,
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statstru text NOT NULL,
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statname text NOT NULL,
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stataddr text NOT NULL,
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longitude numeric(10,7) NOT NULL,
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latitude numeric(10,7) NOT NULL
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);
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COPY pls_fy2017_libraries
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FROM 'C:\YourDirectory\pls_fy2017_libraries.csv'
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WITH (FORMAT CSV, HEADER);
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COPY pls_fy2016_libraries
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FROM 'C:\YourDirectory\pls_fy2016_libraries.csv'
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WITH (FORMAT CSV, HEADER);
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CREATE INDEX libname_2017_idx ON pls_fy2017_libraries (libname);
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CREATE INDEX libname_2016_idx ON pls_fy2016_libraries (libname);
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-- Listing 9-3: Using count() for table row counts
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SELECT count(*)
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FROM pls_fy2018_libraries;
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SELECT count(*)
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FROM pls_fy2017_libraries;
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SELECT count(*)
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FROM pls_fy2016_libraries;
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-- Listing 9-4: Using count() for the number of values in a column
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SELECT count(phone)
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FROM pls_fy2018_libraries;
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-- Listing 9-5: Using count() for the number of distinct values in a column
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SELECT count(libname)
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FROM pls_fy2018_libraries;
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SELECT count(DISTINCT libname)
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FROM pls_fy2018_libraries;
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-- Bonus: find duplicate libnames
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SELECT libname, count(libname)
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FROM pls_fy2018_libraries
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GROUP BY libname
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ORDER BY count(libname) DESC;
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-- Bonus: see location of every Oxford Public Library
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SELECT libname, city, stabr
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FROM pls_fy2018_libraries
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WHERE libname = 'OXFORD PUBLIC LIBRARY';
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-- Listing 9-6: Finding the most and fewest visits using max() and min()
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SELECT max(visits), min(visits)
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FROM pls_fy2018_libraries;
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-- Listing 9-7: Using GROUP BY on the stabr column
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-- There are 55 in 2018.
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SELECT stabr
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FROM pls_fy2018_libraries
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GROUP BY stabr
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ORDER BY stabr;
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-- Bonus: there are 54 in 2017.
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SELECT stabr
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FROM pls_fy2017_libraries
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GROUP BY stabr
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ORDER BY stabr;
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-- Listing 9-8: Using GROUP BY on the city and stabr columns
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SELECT city, stabr
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FROM pls_fy2018_libraries
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GROUP BY city, stabr
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ORDER BY city, stabr;
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-- Bonus: We can count the combos
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SELECT city, stabr, count(*)
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FROM pls_fy2018_libraries
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GROUP BY city, stabr
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ORDER BY count(*) DESC;
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-- Listing 9-9: Using GROUP BY with count() on the stabr column
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SELECT stabr, count(*)
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FROM pls_fy2018_libraries
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GROUP BY stabr
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ORDER BY count(*) DESC;
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-- Listing 9-10: Using GROUP BY with count() on the stabr and stataddr columns
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SELECT stabr, stataddr, count(*)
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FROM pls_fy2018_libraries
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GROUP BY stabr, stataddr
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ORDER BY stabr, stataddr;
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-- Listing 9-11: Using the sum() aggregate function to total visits to
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-- libraries in 2016, 2017, and 2018
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-- 2018
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SELECT sum(visits) AS visits_2018
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FROM pls_fy2018_libraries
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WHERE visits >= 0;
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-- 2017
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SELECT sum(visits) AS visits_2017
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FROM pls_fy2017_libraries
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WHERE visits >= 0;
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-- 2016
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SELECT sum(visits) AS visits_2016
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FROM pls_fy2016_libraries
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WHERE visits >= 0;
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-- Listing 9-12: Using sum() to total visits on joined 2018, 2017, and 2016 tables
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SELECT sum(pls18.visits) AS visits_2018,
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sum(pls17.visits) AS visits_2017,
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sum(pls16.visits) AS visits_2016
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FROM pls_fy2018_libraries pls18
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JOIN pls_fy2017_libraries pls17 ON pls18.fscskey = pls17.fscskey
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JOIN pls_fy2016_libraries pls16 ON pls18.fscskey = pls16.fscskey
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WHERE pls18.visits >= 0
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AND pls17.visits >= 0
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AND pls16.visits >= 0;
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-- Bonus: summing wifi sessions
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SELECT sum(pls18.wifisess) AS wifi_2018,
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sum(pls17.wifisess) AS wifi_2017,
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sum(pls16.wifisess) AS wifi_2016
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FROM pls_fy2018_libraries pls18
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JOIN pls_fy2017_libraries pls17 ON pls18.fscskey = pls17.fscskey
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JOIN pls_fy2016_libraries pls16 ON pls18.fscskey = pls16.fscskey
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WHERE pls18.wifisess >= 0
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AND pls17.wifisess >= 0
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AND pls16.wifisess >= 0;
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-- Listing 9-13: Using GROUP BY to track percent change in library visits by state
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SELECT pls18.stabr,
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sum(pls18.visits) AS visits_2018,
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sum(pls17.visits) AS visits_2017,
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sum(pls16.visits) AS visits_2016,
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round( (sum(pls18.visits::numeric) - sum(pls17.visits)) /
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sum(pls17.visits) * 100, 1 ) AS chg_2018_17,
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round( (sum(pls17.visits::numeric) - sum(pls16.visits)) /
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sum(pls16.visits) * 100, 1 ) AS chg_2017_16
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FROM pls_fy2018_libraries pls18
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JOIN pls_fy2017_libraries pls17 ON pls18.fscskey = pls17.fscskey
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JOIN pls_fy2016_libraries pls16 ON pls18.fscskey = pls16.fscskey
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WHERE pls18.visits >= 0
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AND pls17.visits >= 0
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AND pls16.visits >= 0
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GROUP BY pls18.stabr
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ORDER BY chg_2018_17 DESC;
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-- Listing 9-14: Using HAVING to filter the results of an aggregate query
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SELECT pls18.stabr,
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sum(pls18.visits) AS visits_2018,
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sum(pls17.visits) AS visits_2017,
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sum(pls16.visits) AS visits_2016,
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round( (sum(pls18.visits::numeric) - sum(pls17.visits)) /
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sum(pls17.visits) * 100, 1 ) AS chg_2018_17,
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round( (sum(pls17.visits::numeric) - sum(pls16.visits)) /
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sum(pls16.visits) * 100, 1 ) AS chg_2017_16
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FROM pls_fy2018_libraries pls18
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JOIN pls_fy2017_libraries pls17 ON pls18.fscskey = pls17.fscskey
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JOIN pls_fy2016_libraries pls16 ON pls18.fscskey = pls16.fscskey
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WHERE pls18.visits >= 0
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AND pls17.visits >= 0
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AND pls16.visits >= 0
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GROUP BY pls18.stabr
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HAVING sum(pls18.visits) > 50000000
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ORDER BY chg_2018_17 DESC;
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