So far, we have covered the two ways you can concatenate strings (using function `CONCAT()` or using the `+` sign). We understand that using the `+` sign has limitations. When adding a string to a NULL, your result is a NULL. To avoid the latter, we can use a `CASE` clause.
CASE WHEN condition1 THEN action1 WHEN condition2 THEN action2 ELSE escape_action END
Download the class notes for day 3.