Data commit

Task/Merge-and-aggregate-datasets/SQL/merge-and-aggregate-datasets.sql

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+-- drop tables
+DROP TABLE IF EXISTS tmp_patients;
+DROP TABLE IF EXISTS tmp_visits;
+
+-- create tables
+CREATE TABLE tmp_patients(
+	PATIENT_ID INT,
+	LASTNAME VARCHAR(20)
+);
+
+CREATE TABLE tmp_visits(
+	PATIENT_ID INT,
+	VISIT_DATE DATE,
+	SCORE NUMERIC(4,1)
+);
+
+-- load data from csv files
+/*
+-- Note: LOAD DATA LOCAL requires `local-infile` enabled on both the client and server else you get error "#1148 command is not allowed.."
+LOAD DATA LOCAL INFILE '/home/csv/patients.csv' INTO TABLE `tmp_patients` FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' IGNORE 1 LINES;
+LOAD DATA LOCAL INFILE '/home/csv/visits.csv' INTO TABLE `tmp_visits` FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' IGNORE 1 LINES;
+*/
+
+-- load data hard coded
+INSERT INTO tmp_patients(PATIENT_ID, LASTNAME)
+VALUES
+(1001, 'Hopper'),
+(4004, 'Wirth'),
+(3003, 'Kemeny'),
+(2002, 'Gosling'),
+(5005, 'Kurtz');
+
+INSERT INTO tmp_visits(PATIENT_ID, VISIT_DATE, SCORE)
+VALUES
+(2002, '2020-09-10', 6.8),
+(1001, '2020-09-17', 5.5),
+(4004, '2020-09-24', 8.4),
+(2002, '2020-10-08', NULL),
+(1001, NULL, 6.6),
+(3003, '2020-11-12', NULL),
+(4004, '2020-11-05', 7.0),
+(1001, '2020-11-19', 5.3);
+
+-- join tables and group
+SELECT
+	p.PATIENT_ID,
+	p.LASTNAME,
+	MAX(VISIT_DATE) AS LAST_VISIT,
+	SUM(SCORE) AS SCORE_SUM,
+	CAST(AVG(SCORE) AS DECIMAL(10,2)) AS SCORE_AVG
+FROM
+	tmp_patients p
+	LEFT JOIN tmp_visits v
+		ON v.PATIENT_ID = p.PATIENT_ID
+GROUP BY
+	p.PATIENT_ID,
+	p.LASTNAME
+ORDER BY
+	p.PATIENT_ID;