performance

Thumbnail image for What are CBO and RBO?

What are CBO and RBO?

In large applications that juggle tons of data, it isn’t enough to get a query to run without errors. The query must also perform well – get the results in fastest possible time, using the least possible resources. This is where Oracle’s inbuilt optimizers come into play. Till Oracle 9i, Oracle server provided the options […]

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Thumbnail image for The Smart Way to Check if an Element Exists in a Collection

The Smart Way to Check if an Element Exists in a Collection

When you need to find out if a specific element exists in a collection or not, how do you go about it? Do you loop through the list till you find the value? If that’s what you do, this post is for you.

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Thumbnail image for DISTINCT and How NOT To Use It

DISTINCT and How NOT To Use It

The DISTICT keyword placed next to SELECT restricts the result to unique rows from a query. DISTINCT is also a much abused keyword, often used as a quick fix to bad queries. Take this example from Oracle Applications:

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Thumbnail image for Which is faster – IN or EXISTS?

Which is faster – IN or EXISTS?

A question asked multiple times over on Oracle forums: Which is faster – IN or EXISTS? The short answer, post-Oracle 9i is: Both are pretty much the same! Huh? What about that thumb rule – IN for small inner query, EXISTS for big inner query?

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Thumbnail image for Write Smarter Queries with the SQL WITH Clause

Write Smarter Queries with the SQL WITH Clause

The WITH clause, also known as the subquery factoring clause, was introduced in Oracle 9i as a way to make queries more efficient and readable. Let’s see how WITH works with a basic example.

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