Tag Archives: Oracle 26ai

Oracle 26ai: An Even Closer Look at JOIN TO ONE

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Sometimes the most interesting findings start with a simple question. After publishing my recent post on Oracle 26ai JOIN TO ONE, Iudith Mentzel pointed out something in one of the query transformations that looked perfectly logical – but turned out not to describe what Oracle actually does.

A small test led me one level deeper, from DBMS_UTILITY.EXPAND_SQL_TEXT to the CBO trace, and revealed another interesting aspect of JOIN TO ONE: the way Oracle handles its implicit LEFT OUTER JOIN.

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Oracle 26ai: A Closer Look at JOIN TO ONE

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With Oracle AI Database 23.26.2, Oracle introduced the new JOIN TO ONE syntax. As it happened, just a few weeks later, I was teaching an Oracle 26ai course for data warehouse developers, and we actually managed to take a first look at this brand-new feature. We found it interesting and promising – but it also immediately raised some critical questions. Our conclusion was clear: this deserves a closer look. And that is exactly what this blog post is about.

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