[SQL-195] - Merging Two Rows in SQL

mysql-queries/mysql-store-json/creating-table-example.sql

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+CREATE TABLE Departments ( 
+    id INT PRIMARY KEY NOT NULL, 
+    name VARCHAR(50) NOT NULL, 
+    info JSON 
+);

mysql-queries/mysql-store-json/inserting-json-data.sql

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+INSERT INTO Departments (id, name, info) VALUES 
+(1, 'Computer Science', '{"head": "Dr. Smith", "location": "Building 1", "courses": ["Algorithms", "Data Structures"]}');
+
+INSERT INTO Departments (id, name, info) VALUES 
+(2, 'Mathematics', JSON_OBJECT('head', 'Dr. Johnson', 'location', 'Building 2', 'courses', JSON_ARRAY('Calculus', 'Linear Algebra')));
+
+INSERT INTO Departments (id, name, info) VALUES 
+(3, 'Physics', JSON_OBJECT('head', 'Dr. Clark', 'location', 'Building 3', 'courses', JSON_ARRAY('Quantum Mechanics', 'Thermodynamics')));
+
+SET @head = 'Dr. Miller'; 
+SET @location = 'Building 4'; 
+SET @courses = JSON_ARRAY('Classical Mechanics', 'Electromagnetism'); 
+INSERT INTO Departments (id, name, info) VALUES 
+(4, 'Engineering', JSON_OBJECT('head', @head, 'location', @location, 'courses', @courses));

mysql-queries/mysql-store-json/retrieving-json-data.sql

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+SELECT id, name, info FROM Departments;
+
+SELECT id, name, JSON_EXTRACT(info, '$.head') AS head FROM Departments;
+
+SELECT id, name, info->'$.head' AS head FROM Departments;

mysql-queries/mysql-store-json/updating-json-data.sql

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+UPDATE Departments 
+SET info = JSON_SET(info, '$.head', 'Dr. Parker') 
+WHERE id = 1;
+SELECT id, name, info FROM Departments WHERE id = 1;
+
+UPDATE Departments 
+SET info = JSON_REPLACE(info, '$.location', 'Building 2A')
+WHERE id = 2;
+SELECT id, name, info FROM Departments WHERE id = 2;
+
+UPDATE Departments 
+SET info = JSON_REMOVE(info, '$.courses')
+WHERE id = 3;
+SELECT id, name, info FROM Departments WHERE id = 3;
+
+UPDATE Departments
+SET info = JSON_ARRAY_APPEND(info, '$.courses', 'Artificial Intelligence') 
+WHERE id = 4;
+SELECT id, name, info FROM Departments WHERE id = 4;

sql-queries-3/merging-two-rows/common-table-expression.sql

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+WITH MergedStudent AS (
+     SELECT 
+         2017 AS id,
+         COALESCE(MAX(name), MIN(name)) AS name,
+         COALESCE(MAX(national_id), MIN(national_id)) AS national_id,
+         COALESCE(MAX(birth_date), MIN(birth_date)) AS birth_date,
+         COALESCE(MAX(enrollment_date), MIN(enrollment_date)) AS enrollment_date,
+         COALESCE(MAX(graduation_date), MIN(graduation_date)) AS graduation_date,
+         COALESCE(MAX(gpa), MIN(gpa)) AS gpa
+     FROM 
+         (SELECT * FROM Student WHERE id = 2017
+          UNION ALL
+          SELECT * FROM Student WHERE id = 2008) s
+ )
+ SELECT * FROM MergedStudent;

sql-queries-3/merging-two-rows/updating-with-coalesce.sql

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+SELECT * FROM Student WHERE id IN (1011, 1610);
+
+UPDATE Student AS target
+ SET name = COALESCE(target.name, source.name),
+     national_id = COALESCE(target.national_id, source.national_id),
+     birth_date = COALESCE(target.birth_date, source.birth_date),
+     enrollment_date = COALESCE(target.enrollment_date, source.enrollment_date),
+     graduation_date = COALESCE(target.graduation_date, source.graduation_date),
+     gpa = COALESCE(target.gpa, source.gpa)
+ FROM Student AS source
+ WHERE target.id = 1011 AND source.id = 1610;
+
+DELETE FROM Student WHERE id = 1610;
+
+SELECT * FROM Student WHERE id IN (1011);

sql-queries-3/merging-two-rows/using-insert-into-and-delete.sql

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+INSERT INTO Student (id, name, national_id, birth_date, enrollment_date, graduation_date, gpa)
+ SELECT 
+     1000,
+     COALESCE(s1.name, s2.name),
+     COALESCE(s1.national_id, s2.national_id),
+     COALESCE(s1.birth_date, s2.birth_date),
+     COALESCE(s1.enrollment_date, s2.enrollment_date),
+     COALESCE(s1.graduation_date, s2.graduation_date),
+     COALESCE(s1.gpa, s2.gpa)
+ FROM 
+     (SELECT * FROM Student WHERE id = 1717) s1,
+     (SELECT * FROM Student WHERE id = 1719) s2;
+
+DELETE FROM Student WHERE id IN (1717, 1719);
+
+SELECT * FROM Student WHERE id = 1000;