Merge pull request #230 from daKeshra/main

keshradamora

Author: maibin

sql-queries-5/updating-data-with-joins-in-sql/update-join-with-case.sql

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+-- update data with case case condition
+UPDATE Student 
+SET graduation_date = CASE 
+    WHEN e.semester = 'FALL' THEN '2024-12-15' 
+    WHEN e.semester = 'SPRING' THEN '2024-06-15' 
+    ELSE NULL 
+    END 
+FROM Student AS s 
+JOIN Exam AS e ON s.id = e.student_id;
+
+
+-- display outpt for SPRING semester
+SELECT * FROM Student AS s 
+JOIN Exam AS e ON e.student_id = s.id 
+WHERE e.semester = 'SPRING' 
+LIMIT 10;

sql-queries-5/updating-data-with-joins-in-sql/update-join-with-where.sql

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+-- display top 10 rows of the Student table
+SELECT * FROM Student 
+LIMIT 10;
+
+-- display top 10 result from a join of Exam
+-- and Student table
+SELECT * FROM Exam 
+JOIN Student ON Exam.student_id = Student.id 
+LIMIT 10;
+
+
+-- UPDATE JOIN with WHERE clause
+UPDATE Exam 
+SET e.grade = 'C' 
+FROM Exam AS e 
+JOIN Student AS s ON e.student_id = s.id 
+WHERE s.national_id = 123345566 AND e.grade IS NULL;
+
+
+-- confirm the output
+SELECT * FROM Exam AS e 
+JOIN Student AS s ON e.student_id = s.id 
+WHERE national_id = 123345566;

sql-queries-index/composite-index-in-sql/analyze-composite-index-performance.sql

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+--analyze query performance after assigning composite index
+EXPLAIN SELECT * 
+FROM Student 
+WHERE enrollment_date = '2020-01-15' AND gpa > 4.0;
+
+--optimized query
+SELECT * 
+FROM Student 
+WHERE enrollment_date = '2020-01-15' AND gpa > 4.0;

sql-queries-index/composite-index-in-sql/analyze-query-with-no-composite-index.sql

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+--analyze query performance on column without composite index assigned, using EXPLAIN
+EXPLAIN SELECT * 
+FROM Student 
+WHERE birth_date = '2002-05-15' AND gpa > 3.5;

sql-queries-index/composite-index-in-sql/create-composite-index.sql

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+--show index in table
+SHOW INDEX FROM Student;
+
+--create index on multiple columns
+CREATE INDEX idx_enrollment_gpa 
+ON Student (enrollment_date, gpa);

sql-queries-index/composite-index-in-sql/drop-composite-index.sql

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+--drop the index created
+DROP INDEX idx_enrollment_gpa 
+ON Student;
+
+--Verify if index is dropped
+SHOW INDEX FROM Student;