SQL - Case
SQL CASE is a very unique conditional statement providing if/then/else logic for any ordinary SQL command, such as SELECT or UPDATE . It then provides when-then-else functionality (WHEN this condition is met THEN do_this).
Using the CASE command, we've successfully masked the actual value of the product inventory without actually altering any data. This would be a great way to implement some feature in an online catalog to allow users to check the status of items without disclosing the actual amount of inventory the store currently has in stock.
SQL - Case: Real World Example
As a store owner, there might be a time when you would like to offer sale prices for products. This is a perfect opportunity to write a CASE query and alter the inventory sale
prices at the presentation level rather than actually changing the price inside of the inventory table. CASE provides a way for the store owner to mask the data but still present it in a useful format.
Let's back up a second and pull a listing of our recent orders and join this with the inventory table so that the results contain both the quantity of items purchased and the price from the inventory table. To accomplish this we will need to first write a SQL JOIN query.
SQL Join Query:
In order to provide results that are much clearer, we've moved away from selecting every column with (*). Instead, we've listed each column that will be of use for the next few steps. Also, let's plan on offering a 25 % off sale on these items.Source: www.tizag.com