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| Original file line number | Diff line number | Diff line change |
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| @@ -1,18 +1,95 @@ | ||
| # get the data from the below link | ||
| # https://data.sfgov.org/Public-Safety/Police-Department-Incident-Reports-Historical-2003/tmnf-yvry/data | ||
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| CREATE TABLE police_incident_reports ( | ||
| incident_num VARCHAR(10) PRIMARY KEY, | ||
| category VARCHAR(50), | ||
| descript VARCHAR(100), | ||
| dayofweek VARCHAR(10), | ||
| date DATE, | ||
| time TIME, | ||
| pd_district VARCHAR(10), | ||
| resolution VARCHAR(50), | ||
| address VARCHAR(100), | ||
| x NUMERIC(9,6), | ||
| y NUMERIC(9,6), | ||
| location POINT, | ||
| pd_id BIGINT | ||
| ); | ||
| -- Active: 1688066368502@@pg-db@5432@sfpolice | ||
| -- get the data from the below link | ||
| -- https://data.sfgov.org/Public-Safety/Police-Department-Incident-Reports-Historical-2003/tmnf-yvry/data | ||
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| -- make sure you have a connection created using the vscode extension | ||
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| -- Exploring data | ||
| -- 1. How many police districts are there? | ||
| SELECT COUNT(DISTINCT pddistrict) FROM police_incident_reports; | ||
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| -- How many neighborhoods are there? | ||
| SELECT COUNT(DISTINCT "Neighborhoods 2") FROM police_incident_reports; | ||
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| -- How many incidents by neighborhood? | ||
| SELECT "Neighborhoods 2", COUNT(*) AS COUNT FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*); -- Try to visualize in pgadmin | ||
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| -- Check the min and max number of incidents by neighborhood | ||
| SELECT MAX(s.COUNT) AS MAX, MIN(s.COUNT) AS MIN, AVG(s.COUNT) As AVG | ||
| FROM ( | ||
| SELECT "Neighborhoods 2" AS Neighborhood, COUNT(*) FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*) | ||
| ) s; | ||
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| -- KPIs for incidents by neighborhood | ||
| -- declare min, max, and avg as variables | ||
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| CREATE OR REPLACE FUNCTION avergae_no_of_incidents() | ||
| RETURNS INT | ||
| AS $$ | ||
| DECLARE | ||
| average integer := 0; | ||
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| BEGIN | ||
| SELECT AVG(s.COUNT) INTO average | ||
| FROM ( | ||
| SELECT "Neighborhoods 2" AS Neighborhood, COUNT(*) FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*) | ||
| ) s; | ||
| return average; | ||
| END; | ||
| $$ LANGUAGE plpgsql; | ||
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| select avergae_no_of_incidents() | ||
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| SELECT "Neighborhoods 2" AS Neighborhood, COUNT(*), | ||
| CASE | ||
| WHEN COUNT(*) > avergae_no_of_incidents() THEN 'High' | ||
| ELSE 'LOW' | ||
| END AS State | ||
| FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*) | ||
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| -- replace the function with a subquery | ||
| SELECT "Neighborhoods 2" AS Neighborhood, COUNT(*), | ||
| CASE | ||
| WHEN COUNT(*) > (SELECT AVG(s.COUNT) FROM (SELECT "Neighborhoods 2" AS Neighborhood, COUNT(*) FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*)) s) THEN 'High' | ||
| ELSE 'LOW' | ||
| END AS State | ||
| FROM police_incident_reports GROUP BY "Neighborhoods 2" order by COUNT(*) | ||
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| -- Data Cleanup | ||
| -- Deduplication using Group By and Distinct | ||
| -- Data Cleaning using CASE WHEN and LIKE | ||
| -- Data Cleaning using TRIM, UPPER, LOWER, INITCAP, SUBSTRING, POSITION, LENGTH, CONCAT, REPLACE, TRANSLATE, REGEXP_REPLACE, REGEXP_MATCHES, REGEXP_SPLIT_TO_ARRAY, REGEXP_SPLIT_TO_TABLE, SPLIT_PART, TO_CHAR, TO_NUMBER, TO_DATE, TO_TIMESTAMP, TO_TIMESTAMP_TZ, TO_JSON, TO_JSONB, TO_ASCII, TO_HEX, TO_BASE64, TO_REGCLASS, TO_REGPROC, TO_REGPROCEDURE, TO_REGOPER, TO_RE | ||
| -- Type Conversion using CAST and :: | ||
| SELECT pd_id FROM police_incident_reports LIMIT 3; -- it's bigint now | ||
| SELECT pd_id*2 FROM police_incident_reports LIMIT 3; -- it's bigint now | ||
| SELECT (pd_id::varchar) + 2 FROM police_incident_reports LIMIT 3; -- Error as it's varchar now | ||
| SELECT CAST(pd_id AS varchar) * 2 FROM police_incident_reports LIMIT 3; -- Error as it's varchar now | ||
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| -- split string | ||
| SELECT split_part(CAST(pd_id AS varchar), '0', 1) FROM police_incident_reports LIMIT 3; -- can be split now as it's string | ||
| SELECT split_part(pd_id, '0', 1) FROM police_incident_reports LIMIT 3; -- Error as it's bigint now and cannot be split | ||
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| -- Window Functions | ||
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| select * from public.police_incident_reports limit 5; | ||
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| select category, count(incidentnum) from police_incident_reports group by category | ||
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| --What if I want to display the count of incidents by category but still see the rest of the columns in the table? | ||
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| select category, pddistrict, count(incidentnum) from police_incident_reports group by category, pddistrict --This will not work as this still shows the breakdown of the count by category then pddistrict | ||
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| -- Must use the window function | ||
| select *, count(incidentnum) over() from police_incident_reports | ||
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| -- take a window of the full table | ||
| Select category, pddistrict, descript, count(incidentnum) over() from police_incident_reports | ||
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| -- change the scope of the window to the category alone | ||
| Select category, pddistrict, descript, count(incidentnum) over(partition by category) from police_incident_reports |