- The subquery `SELECT DISTINCT p FROM bst` includes a `NULL` value because there is a row `(15, NULL)` in the table. - When SQL evaluates `NOT IN`, it checks if the value does **not** exist in the ...

Abstract: The lack of information within relational databases expressed as NULL values presents a problem in ensuring the quality of data and the information retrieved by SQL queries. This is so ...

Null or nonexistent data gets complicated when the application expects a data value and gets nothing or unexpected values; that's when you must perform coding that properly handles these situations to ...