When SQL Has Nothing to Say: Understanding NULLs

NULL in SQL carry different meanings; missing value unknown value no value inapplicable data customer_id customer_name contact 101 Alice 0712345678 102 Brian NULL 103 Carol 0798765432 You shouldn't interpret NULL as; 0 (zero) '' (empty string) blank space Using IS NULL, IS NOT NULL to find NULLs Since NULL is not equal to zero or an empty string,...