Myth: Oracle Cannot Index NULL


The source of this myth is rather easy to understand when you look at the correctly expressed statement:

The Oracle database does not include rows into an index if all indexed columns are NULL.

The difference between the myth and the reality is small—it seems that the myth is a sloppy form of the truth.

The truth is that NULL can be indexed by adding another not nullable column to the index:

CREATE INDEX with_null ON table_name (nullable_column, '1');

Read Section 6.1 for the full story.

About the Author

Photo of Markus Winand
Markus Winand tunes developers for high SQL performance. He also published the book SQL Performance Explained and offers in-house training as well as remote coaching at http://winand.at/

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