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What are Optimizer Statistics? Databases for Developers: Performance #2

To choose an execution plan, the optimizer needs to estimate how many rows it'll read from each table. But what does it base these estimates on? The table statistics! Watch this video to learn what these are and how they affect execution plans. Need help with SQL? Ask us over on AskTOM: https://asktom.oracle.com Twitter:   / chrisrsaxon   Daily SQL Twitter tips:   / sqldaily   All Things SQL blog: https://blogs.oracle.com/sql/ Test your SQL Skills on the Oracle Dev Gym: https://devgym.oracle.com/ ============================ The Magic of SQL with Chris Saxon Copyright © 2020 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.