Merging Two Rows in SQL

Author: GeoSegun

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;