by Markus Winand.

The Oracle Database 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 Indexing NULL for the full story.

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Markus Winand teaches efficient SQL—inhouse and online. He minimizes the development time using modern SQL and optimizes the runtime with smart indexing. His book entitled SQL Performance Explained has become standard reading.

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“Use The Index, Luke!” by Markus Winand is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.
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