NULL is a fickle beast, and for the people not accustomed to how it works in SQL, it can create many problems (read: incorrect data output). This is especially true for those coming from ...

- When SQL evaluates `NOT IN`, it checks if the value does **not** exist in the list returned by the subquery. - If the subquery contains a `NULL`, any comparison with `NULL` results in an unknown ...

Is your SQL drawing a blank? It’s NULL a surprise! The title of this post is a play on words, but very appropriate. We are going to discuss the inconsistent results, as well as performance ...

For example, comparing NULL to any value, including another NULL, always returns unknown, not true or false. Secondly, you must grasp the impact of NULL on various SQL operations. Comparisons ...

Design for null. “Expect that you will get null results and collect the data that allows you to explain it,” Hill urges. At the end of a recent study, her team interviewed teachers about what made ...