John Watson's blog

Compression test, 12cR2

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Just how effective is Hybrid Columnar Compression? This test shows that HCC is impressive, but that thought needs to be put into choice of compression algorithm.

12cR2 lots of new instance parameters

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Comparing database 12cR1 release 12.1.0.2 to 12cR2 release 12.2.0.0.3, I see these new parameters:

12cR2 new feature: online table move

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Move a table without locks and without breaking indexes. That's pretty cool.

Is row-by-row processing really slow-by-slow? Emphatically: YES

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Developers who come to Oracle with a background in procedural languages sometimes do not understand how efficient SQL's set oriented processing can be. This little demonstration should convince them: never use PL/SQL when SQL will do.

How to change column order when using SELECT *

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We all know that using SELECT * is bad programming. One reason is that you cannot control the order in which columns are returned. Well, you can in release 12c.

Oracle 12cR2 - the next release, cloud only?

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We are all waiting for database release 12.2 - but you won't get it on your own hardware.

How indexes can degrade performance

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Indexes may improve the performance of SELECT statements, but what about DML? This simple demo shows how bad they can be.

Roles , PL/SQL, and ORA-00942: table or view does not exist

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Many developers find that their code fails with ORA-942, but when they test the failing statement from the SQL> prompt, it works. Why, and what can you do to fix it?

Partitioning and Oracle Standard Edition

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I first came across partitioning with release 7, when it didn't exist. Like many DBAs, I simulated it by writing a lot of application code. You can still do this – and you may have to if you haven't bought Enterprise Edition plus the partitioning option. Here's another way to do it, with partitioned views.

When is an index access path better than a full table scan?

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The cost based optimizer makes decisions that can be hard to understand. One of the hardest may be why it chooses indexed or scan access paths: a burning question for many DBAs.

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