What does this SQL do?
SELECT COALESCE(FirstName + ' ' + MiddleName, FirstName) + ' ' + LastName FROM Customer
If MiddleName is NULL, then FirstName + '' + MiddleName would be NULL, and so would return FirstName + ' ' + LastName.
If MiddleName is not NULL, it would return FirstName + ' ' +MiddleName + ' ' + LastName
