Performance

Performance tuning concepts and guidelines for the Oracle database.

DBMS_REDEFINITION for online table redefinition

DBMS_REDEFINITION: Convert Non-Partitioned Table to Partitioned [pre 12.2]

Partitioning a non-partitioned table in an Oracle pre-12.2 database, using DBMS_REDEFINITION built-in methods. Scripts and demo.

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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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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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Passing Parameter by Value

NOCOPY Parameter Hint in PL/SQL

Before we get to understanding the NOCOPY parameter hint in PL/SQL, it would help to first look at PL/SQL parameter modes and the ways in which they pass values in and out of a subprogram. PL/SQL subprograms have three parameter modes:

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DISTINCT Keyword in Oracle

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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Oracle SQL: IN vs 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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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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Why Should You Use PL/SQL Packages

6 Reasons Why You Should Use PL/SQL Packages

When stored procedures/functions can exist standalone, why have packages at all? This article tells you the benefits of using PL/SQL packages.

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