added example files for aggregators and random

tasks/aggregators.sql

@@ -0,0 +1,12 @@
+USE tutorial;
+
+SELECT count(annualSalaryGrossEUR_Amount) FROM Employee;
+SELECT sum(annualSalaryGrossEUR_Amount) FROM Employee;
+SELECT avg(annualSalaryGrossEUR_Amount) FROM Employee;
+
+SELECT Department.name, round(avg(annualSalaryGrossEUR_Amount), 2) AS salary
+    FROM Employee
+    LEFT JOIN Department ON Employee.departmentId = Department.id
+    GROUP BY departmentId
+    HAVING salary > 48000
+    ORDER BY salary DESC;

tasks/pricePerSqm.sql

@@ -0,0 +1,3 @@
+USE tutorial;
+
+SELECT round(EUR_rentalAmount / Room.M2_area, 2) AS 'price per m²' FROM Room;

tasks/rands.sql

@@ -0,0 +1 @@
+SELECT floor(rand() * (8.0 - 2.0) + 2.0);