Add SQL queries for retrieving, filtering, and sorting data

Added SQL queries for the following tasks:
- Retrieving specific columns (checkNumber, paymentDate, amount) from the payments table.
- Filtering and sorting orders by status 'In Process' and orderDate.
- Displaying employee details for the job title 'Sales Rep', ordered by employeeNumber.
- Fetching all columns from the offices table.
- Sorting products by buyPrice and limiting results to 5 records.

Author: augusto-mate

answers.sql

@@ -1,35 +1,47 @@
 -- 1. Retrieve checkNumber, paymentDate, and amount from the payments table
--- This query selects specific columns from the payments table: checkNumber, paymentDate, and amount.
+-- In this query, we are selecting the columns 'checkNumber', 'paymentDate', and 'amount' from the 'payments' table.
+-- These columns store information about payment transactions, such as the check number, the date of payment, and the amount paid.
 
 SELECT checkNumber, paymentDate, amount
 FROM payments;
 
+
 -- 2. Retrieve orderDate, requiredDate, and status of orders with 'In Process' status
--- The query filters orders with the status 'In Process' and sorts them in descending order of orderDate.
+-- This query is filtering orders with the status 'In Process'. 
+-- The 'status' column indicates the current state of the order. We then sort the results by 'orderDate' in descending order 
+-- to display the most recent orders first.
 
 SELECT orderDate, requiredDate, status
 FROM orders
-WHERE status = 'In Process'
-ORDER BY orderDate DESC;
+WHERE status = 'In Process'  -- Filter only orders that are still 'In Process'
+ORDER BY orderDate DESC;  -- Sort results by orderDate in descending order
+
 
 -- 3. Retrieve firstName, lastName, and email of employees with the job title 'Sales Rep'
--- The query filters employees with the job title 'Sales Rep' and orders the results by employeeNumber in descending order.
+-- This query filters employees based on their job title ('Sales Rep').
+-- We are interested in employees working in sales, and we order the results by 'employeeNumber' in descending order, 
+-- which helps to see the most recently added employees first.
 
 SELECT firstName, lastName, email
 FROM employees
-WHERE jobTitle = 'Sales Rep'
-ORDER BY employeeNumber DESC;
+WHERE jobTitle = 'Sales Rep'  -- Filter employees who have 'Sales Rep' as their job title
+ORDER BY employeeNumber DESC;  -- Sort results by employeeNumber in descending order
+
 
 -- 4. Retrieve all columns and records from the offices table
--- This query selects all columns and records from the offices table without applying any filters.
+-- This query retrieves all columns (*) and all records from the 'offices' table. 
+-- The 'offices' table contains information about the company's office locations, such as city, country, and phone number.
+
+SELECT * 
+FROM offices;  -- Retrieve all columns from the offices table
 
-SELECT *
-FROM offices;
 
 -- 5. Retrieve productName and quantityInStock from the products table
--- The query sorts the results by buyPrice in ascending order and limits the output to 5 records.
+-- In this query, we retrieve the 'productName' and 'quantityInStock' from the 'products' table. 
+-- We are also sorting the results by 'buyPrice' in ascending order, which helps to see the cheapest products first. 
+-- Finally, we limit the output to only the first 5 records.
 
 SELECT productName, quantityInStock
 FROM products
-ORDER BY buyPrice ASC
-LIMIT 5;
+ORDER BY buyPrice ASC  -- Sort results by 'buyPrice' in ascending order
+LIMIT 5;  -- Limit the result to only the first 5 records