SQL Logic


In this article, I will discuss the history and thinking behind several types of logic that are typically associated with writing relational database code. Because of how relational databases implement NULLs, it definitely can make some processes more complex than expected by may programmers (inexperienced and experienced alike!)

Three Valued Logic

Missing or UNKNOWN values have been a problem in data modeling and statistics long before there was SQL. One of the best solutions has been to create a category for “miscellaneous”, “UNKNOWN”, “N/A (Not applicable), “other”, “TBD (to be determined)” and so forth. When Dr. Codd was designing the