The ISNULL() function
The COALESCE() function
10. Using COALESCE() with other functions
The NULLIF() function


Nice! You can also use COALESCE() with other functions and operations, such as + concatenation, multiplication, etc. Take a look as we use + concatenation to show two columns as one:

  COALESCE(Category, N'unknown category')
  + ': ' 
  + COALESCE(Type, N'unknown type')
  AS CategoryType
FROM Product;

In the above query fragment, a NULL Category or Type value is replaced with an appropiate message, but we can still see the Type when the Category is NULL (and vice versa).

Do you remember how even one NULL in the whole expression will result in a NULL as an outcome for it? Thanks to COALESCE, this isn't a problem anymore.


Show the following sentence:

Product X is made in Y.

X is the product Name and Y is the ProductionArea. If the name is not provided, write N'unknown name' instead. If the production area is not provided, write N'unknown area'. Name the column Origin.

Stuck? Here's a hint!

Use + to create the sentence. Remember about the period at the end of the sentence.