add queries

queries.sql

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+-- SELECTION OF RECORDS USING * WILDCARD
+-- These queries display all information from all tables in the database:
+SELECT * FROM researchers;
+SELECT * FROM students;
+SELECT * FROM courses;
+SELECT * FROM research_proposals;
+SELECT * FROM student_grades;
+
+-- DELETION QUERY
+-- This query deletes the record with res_id 1 from the researchers table.
+DELETE FROM researchers WHERE res_id = 1;
+
+-- AGGREGATE FUNCTION MAKING USE OF GROUP
+-- This query performs an inner join between the researchers and research_proposals tables on the res_id column.
+-- The result includes the res_home_uni column from the researchers table, as well as the required_amount column from the research_proposals table.
+-- The query then groups the results by the res_home_uni column and calculates the average required_amount for each group.
+SELECT res_home_uni, AVG(required_amount) FROM researchers
+ INNER JOIN research_proposals ON researchers.res_id = research_proposals.researcher_id
+ GROUP BY res_home_uni;
+
+-- SELECTION OF RECORD(S) USING WILDCARD.
+-- This query selects all columns from the students table where the stu_first_name column contains the letter "e".
+-- The query uses the LIKE operator with the wildcard pattern '%e%' to match any first name that contains the letter "e".
+SELECT * FROM students WHERE stu_first_name LIKE '%e%';
+
+-- INNER JOIN BETWEEN 2 TABLES
+-- This query performs an inner join between the researchers and research_proposals tables on the res_id column.
+-- The result includes all columns from both tables for the matching records.
+SELECT * FROM researchers
+ INNER JOIN research_proposals ON researchers.res_id = research_proposals.researcher_id;
+
+
+-- LEFT OUTER JOIN BETWEEN 2 TABLES
+-- This query performs a left outer join between the researchers and research_proposals tables on the res_id column.
+-- The result includes all columns from the researchers table, as well as the matching columns from the research_proposals table.
+-- Records from the researchers table that do not have a matching record in the research_proposals table will be NULL.
+SELECT * FROM researchers
+ LEFT OUTER JOIN research_proposals ON researchers.res_id = research_proposals.researcher_id;
+
+-- RIGHT JOINS DEMONSTRATE THE TABLES AND RELATIONS IMPLEMENTED
+-- This query performs a right join between the researchers and research_proposals tables on the res_id column.
+-- The result includes all columns from the research_proposals table, as well as the matching records from the researchers table.
+-- Records from the researchers table that do not have a matching record in the research_proposals table will be NULL.
+SELECT * FROM researchers
+ RIGHT JOIN research_proposals ON researchers.res_id = research_proposals.researcher_id;