London_9_Lovelace - Howard_Sun - SQL- week 1

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.
 

2-classes-db/task.md

@@ -21,31 +21,49 @@ To submit this homework write the correct commands after each question.
 
 ### 1. Show the date, transaction_no, description and amount for those transactions whose amount is between £30,000 and £31,000.
 ```sql
-
+SELECT date,transaction_no, description, amount 
+FROM spends 
+WHERE amount BETWEEN 30000 AND 31000;
 ```
 ### 2. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'fee'.
 ```sql
-
+SELECT date,transaction_no,supplier_inv_no,description,amount 
+FROM spends
+WHERE description LIKE '%fee%';
 ```
 ### 3. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'Fee'.
 ```sql
-
+ SELECT date,transaction_no,supplier_inv_no,description,amount
+ FROM spends
+ WHERE description LIKE '%Fee%';
 ```
 ### 4. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'fee' (case insensitive). You will need to search 'https://www.postgresql.org/docs/' to solve this.
 ```sql
-
+ SELECT date,transaction_no,supplier_inv_no,description,amount
+ FROM spends
+ WHERE description LIKE LOWER('%fee%');
 ```
 ### 5. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose amount is £25,000, £30,000, £35,000 or £40,000.
 ```sql
-
+ SELECT date,transaction_no,supplier_inv_no,description,amount
+ FROM spends
+ WHERE amount IN (25000,30000,35000,40000);
 ```
 ### 6. Show the date, the supplier_id, the description and the amount for transactions with the expense area of 'Better Hospital Food'. You could do a query to get the expense_area_id first then do a query to find the dates, supplier_ids and amounts. But it would be better to do this all in one query by linking the tables together using INNER JOINs.
 ```sql
-
+ SELECT date,supplier_id,description,amount
+ FROM spends 
+ INNER JOIN expense_areas
+ ON spends.id = expense_areas.id
+ WHERE expense_areas.id = (SELECT id FROM expense_areas WHERE expense_area = 'Better Hospital Food');
 ```
 ### 7. Show the date, supplier name, description and amount for transactions with the expense area of 'Better Hospital Food'. You will need to INNER JOIN another table to be able to do this.
 ```sql
-
+ SELECT date,supplier_id,description,amount
+ FROM spends
+ INNER JOIN suppliers
+ ON spends.id = suppliers.id
+ WHERE suppliers.id = (SELECT id FROM suppliers WHERE supplier = 'Better Hospital Food');
 ```
 ### 8. We have just received a late invoice for April! Add a new row to the spends table:
     dated 1st April 2021
@@ -56,11 +74,14 @@ To submit this homework write the correct commands after each question.
     the expense area is 'ICT Contingency' (id 18)
     for £32,000.
 ```sql
-
+ INSERT INTO spends (date, description, transaction_no, supplier_inv_no, supplier_id, expense_type_id, expense_area_id, amount)
+ VALUES ('2021-04-01', 'Computer Hardware Dell', 38104091, '3780119655', 16, 7, 18, 32);
 ```
 ### 9. If you examine the dates in the data, you will see they all are dated either 1st march 2021 or 1st April 2021. So if we group on the the date, there will only be two groups. Show the date and the total amount spent on that date for these two dates by using a GROUP BY clause.
 ```sql
-
+ SELECT date, SUM(amount)
+ FROM spends
+ GROUP BY date;
 ```
 ### 10. (optional) Great we now know the monthly spend. But it didn't look that good. So I've changed my SELECT query to output this instead:
 ```
@@ -73,7 +94,9 @@ To submit this homework write the correct commands after each question.
 Can you work out how to do this?
 
 ```sql
-
+ SELECT MONTH(date) AS Month, SUM(amount) AS Monthly Spend
+ FROM spends
+ GROUP BY MONTH(date);
 ```
 
 When you have finished all of the questions - open a pull request with your answers to the `SQL-Coursework-Week1` repository.