SQL Using Northwind Database.

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$1.$ Write a query to identify the top $5$ Most Frequent Customers who have placed the highest number of orders.

$2.$ Write a query to find the Average Delivery Time by Region. Please follow the calculation to find the average delivery time $($days between OrderDate and ShippedDate$)$ by region $($DF$,$ SP$,$ AK$,$ WA$)$

$3.$ Write a query to retrieve the latest customer order date for each customer in a database. In other words, you will Identify the last order date for each customer. Pick on the listed customer id$..$

$4.$ Write a query to determine the average order amount for each product category. You will list all the categories.

$5.$ Write a query to Identify products that have not recorded any sales, i$.$e$.,$ Products with NO Sales record.

$6.$ write a query to find employees with no record of managing$$orders$.$

$7.$ Write a query to determine each product$$s share of total sales within its category, expressed as a percentage, considering only products with sales exceeding $50,000.$

$8.$ Write a query to evaluate the year$-$over$-$year rate at which customers continue their engagement.

$9.$ Create a query to determine which five days of the week experience the greatest volume of orders.

$10.$ Write a query to find the top$-$selling product by quantity for each of the following suppliers: 'Gai pturage,$\text{'}$ 'Pavlova, Ltd$.,\text{'}$ and 'Exotic Liquids.$\text{'}$