dezoomcamp exercises

01_week.sql

/*
 * There are two question before these that don not require much code,
 * so only the SQL related answers are written below.
 */


/* See the data */

SELECT 
	* 
FROM 
	yellow_taxi_data 
LIMIT 
	20;


/* 
 * Question 3. Count records  
 * How many taxi trips were there on January 15? 
 * Consider only trips that started on January 15. 
 */

SELECT 
	COUNT(*) 
FROM 
	yellow_taxi_data
WHERE
	DATE_TRUNC('day', tpep_pickup_datetime) = '2021-01-15'; 
  

/*
 * Question 4. Average Find the largest tip for each day. 
 * On which day it was the largest tip in January? 
 * Use the pick up time for your calculations. (note: it's not a typo, it's "tip", not "trip")
 */

/* Largest tip for each day */
SELECT 
	MAX(tip_amount) AS max_tip, DATE_TRUNC('day', tpep_pickup_datetime) AS tpep_pickpup_day 
FROM 
	yellow_taxi_data
GROUP BY 
	tpep_pickpup_day;

	

/* On which day it was the largest tip in January? */
SELECT 
	MAX(tip_amount) AS max_tip, DATE_TRUNC('day', tpep_pickup_datetime) AS tpep_pickpup_day 
FROM 
	yellow_taxi_data
WHERE 
	DATE_TRUNC('month', tpep_pickup_datetime) = '2021-01-01'
GROUP BY 
	tpep_pickpup_day
ORDER BY 
	max_tip DESC
LIMIT 
	1;




/*
 * Question 5. Most popular destination
 * What was the most popular destination for passengers picked up 
 * in central park on January 14?
 * Use the pick up time for your calculations.
 * Enter the zone name (not id). If the zone name is unknown (missing), write "Unknown"  
 */

SELECT 
  DATE_TRUNC('day', taxi.tpep_pickup_datetime) as pick_up_day, 
  pick_up."Zone" AS "pick_up_loc",
  drop_off."Zone" AS "drop_off_loc",
  count(pick_up."Zone") AS "pick_up_count",
  count(drop_off."Zone") AS "drop_off_count"
FROM 
	yellow_taxi_data taxi,
	zones pick_up,
	zones drop_off
WHERE 
	taxi."PULocationID" = pick_up."LocationID" AND
	taxi."DOLocationID" = drop_off."LocationID" AND
	DATE_TRUNC('day', taxi.tpep_pickup_datetime) = '2021-01-14' AND
	pick_up."Zone" = 'Central Park'
GROUP BY 
	pick_up_day, pick_up."Zone", drop_off."Zone"
ORDER BY 
	drop_off_count DESC
LIMIT 
	1;


/*
 * Question 6
 * What's the pickup-dropoff pair with the largest 
 * average price for a ride (calculated based on `total_amount`)?
 * Enter two zone names separated by a slash. For example:
 * "Jamaica Bay / Clinton East"
 * If any of the zone names are unknown (missing), write "Unknown". For example, "Unknown / Clinton East".  
 */



SELECT 
  AVG(total_amount) as avg_price, 
  CASE 
  	WHEN 
  		(pick_up."Zone" IS NOT NULL AND drop_off."Zone" IS NULL) 
  	THEN 
  		CONCAT( pick_up."Zone", '/', 'Unknown') 
  	WHEN 
  		(pick_up."Zone" IS NULL AND drop_off."Zone" IS NOT NULL) 
  	THEN 
  		CONCAT( 'Unknown', '/', drop_off."Zone") 
  	WHEN 
  		(pick_up."Zone" IS NULL AND drop_off."Zone" IS NULL) 
  	THEN 
  		CONCAT( 'Unknown', '/', 'Unknown') 
	ELSE 
	   CONCAT( pick_up."Zone", '/', drop_off."Zone") 
   END AS "loc_pair"
FROM 
	yellow_taxi_data taxi,
	zones pick_up,
	zones drop_off
WHERE 
	taxi."PULocationID" = pick_up."LocationID" AND
	taxi."DOLocationID" = drop_off."LocationID"
GROUP BY 
	loc_pair
ORDER BY 
	avg_price DESC
LIMIT 
	1;