London_10-Saliha_Popal/Databases-Homework /Week1

week-1/mandatory/1-reading/task.md

@@ -6,5 +6,5 @@
 2.  Study the PostgreSQL documentation that covers provided functions and operators in SQL (https://www.postgresql.org/docs/current/functions.html):
     1.  Read the String Functions and Operators section.
     2.  Read the Date/Time Functions and Operators section.
-3.  Study the build-hotel.sql script used to create the sample database.  Compare it with the struture of the tables themselves.
+3.  Study the build-hotel.sql script used to create the sample database.  Compare it with the structure of the tables themselves.
 

week-1/mandatory/2-classes-db/task.md

@@ -19,18 +19,52 @@ If you haven't completed all the exercises from this lesson then do that first.
 
 ### Tasks
 1.  Which rooms have a rate of more than 100.00?
+
+select room_type, rate from rooms where rate > 100;
+
 2.  List the reservations that have a checkin date this month and are for more than three nights.
+
+select * from reservations where extract(month from checkin_date) = extract(month from current_date) and checkout_date - checkin_date > 3;
+
 3.  List all customers from cities that begin with the letter 'M'.
 
+select * from customers where city like 'M%';
+
+
 Insert some new data into the room_types and rooms tables, querying after each stage to check the data, as follows:
 
 4.  Make a new room type of PENTHOUSE with a default rate of £185.00
+
+insert into room_types (room_type, def_rate) values('PENTHOUSE', 185);
+
 5.  Add new rooms, 501 and 502 as room type PENTHOUSE and set the room rate of each to the default value (as in the new room type).
+
+insert into rooms (room_no, room_type, rate) values(501, 'PENTHOUSE', 185), (502, 'PENTHOUSE', 185);
+
 6.  Add a new room 503 as a PREMIER PLUS type similar to the other PREMIER PLUS rooms in the hotel but with a room rate of 143.00 to reflect its improved views over the city.
 
+insert into rooms (room_no, room_type, rate) values(503, 'PREMIER PLUS', 143);
+
 Using what you can learn about aggregate functions in the w3schools SQL classes (or other providers), try:
 
 7.  The hotel manager wishes to know how many rooms were occupied any time during the previous month - find that information.
+
+select count(room_no) as occupied_rooms
+from reservations
+  where checkin_date <= date_trunc('month', current_date) - interval '1 day'
+  and checkout_date >= date_trunc('month', current_date - interval '1 month');
+
+
 8.  Get the total number of nights that customers stayed in rooms on the second floor (rooms 201 - 299).
+
+select sum(checkout_date-checkin_date) as nights from reservations where room_no between 201 and 209;
+
 9.  How many invoices are for more than £300.00 and what is their grand total and average amount?
+
+select count(*), sum(total), avg(total) from invoices where total > 300 ;
+
 10.  Bonus Question: list the number of nights stay for each floor of the hotel (floor no is the hundreds part of room number, e.g. room **3**12 is on floor **3**)
+
+select count(checkout_date - checkin_date) as nights from reservation where room_no between 101 and 503 group by floor order by floor_no;
+
+select floor(room_no / 100) as floor_no, sum(checkout_date - checkin_date) as nights from reservations where room_no between 101 and 503 group by floor(room_no / 100) order by floor_no;