rownum

Thumbnail image for 15 Things You Should Know about the ORDER BY Clause

15 Things You Should Know about the ORDER BY Clause

What is the precedence of sorting in a multi-column ORDER BY? How does ORDER BY sort nulls? What does ORDER SIBLINGS BY do? Answers to these questions and more about Oracle’s ORDER BY clause.

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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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Thumbnail image for The Magic Of ROWNUM

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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Thumbnail image for Selecting ODD or EVEN rows from a table

Selecting ODD or EVEN rows from a table

Question: How can I select only the even/odd rows from an Oracle table? Answer: Talking of “even or odd rows” is meaningless in Oracle until you have ordered the rows.

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