NULL Handling in SQLite

NULL Handling in SQLite

NULL Handling in SQLite Versus Other Database Engines

The goal is to make SQLite handle NULLs in a standards-compliant way. But the descriptions in the SQL standards on how to handle NULLs seem ambiguous. It is not clear from the standards documents exactly how NULLs should be handled in all circumstances.

So instead of going by the standards documents, various popular SQL engines were tested to see how they handle NULLs. The idea was to make SQLite work like all the other engines. An SQL test script was developed and run by volunteers on various SQL RDBMSes and the results of those tests were used to deduce how each engine processed NULL values. The original tests were run in May of 2002. A copy of the test script is found at the end of this document.

SQLite was originally coded in such a way that the answer to all questions in the chart below would be "Yes". But the experiments run on other SQL engines s