Thumbnail image for The Special DUAL Table in Oracle

The Special DUAL Table in Oracle

DUAL is a special one-row, one-column table in Oracle data dictionary. Some trivia about DUAL table in Oracle and best practices for using DUAL in SQL.

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The Magic Of ROWNUM

Pseudocolumn ROWNUM in Oracle, which assigns a number to every row returned by a query, has properties so interesting it almost looks like magic!

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The Difference Between Views and Materialized Views

Key differences between views and materialized views in Oracle, with guidelines to help you decide if a specific scenario needs a view, a materialized view, or neither.

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Oracle Views

20 Things You Should Know About Oracle Views

This one just might fail the Duck Test. It looks like a table, acts like a table, responds to SQLs like a table – but it is NOT a table. Learn about features and best practices for dealing with Oracle views.

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How to Reset a Sequence in Oracle

Oracle does not a have ready-made command to restart a sequence. But with this simple workaround, you can reset a sequence in Oracle.

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The Difference Between UNION and UNION ALL

Both UNION and UNION ALL concatenate the result sets of two separate SQLs. Where they differ is in the way they handle duplicates.

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How to Find Duplicate Records in a Table

Query to find all duplicate records in an Oracle table. Typically required in scenarios where duplicate rows in a table are to be identified and then deleted.

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An Easy Guide to PL/SQL Collections

Oracle PL/SQL collections are of three types: Index By Tables, Nested Tables, Varrays. Here’s a comparison chart of the types of PL/SQL collections based on parameters such as size, ease of modification, and persistence.

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What is CTAS?

When you want to base your Oracle table structure and data on an existing table, you use CTAS. Learn what that acronym means.

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Rename Column in an Oracle Table

Rename Column in an Oracle Table

Post 9i Oracle gives you a direct command to rename column in an Oracle table. Here’s how to do it. Bonus: workaround to rename a table column in older versions of Oracle.

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