Comparisons with NULL
Functions with NULL
COALESCE to the rescue
Instruction
Perfect! As you can see, we got a NULL when one of the concatenated columns was a NULL.
The same goes for mathematical operators: +, -, *, /. Adding a NULL value to something will return NULL. Similarly, multiplying two values, of which one is NULL, will always return NULL.
Exercise
A new tax has been imposed on all the products, which is 2% of the final price. Show all product names with their old price (column name old_price) and new price rounded to two decimal points (column name new_price). Note what happens when there is no price.
Stuck? Here's a hint!
To round x to two decimal points, you can use the ROUND() function in the following way:
ROUND(x, 2)
