Select (SQL): Difference between revisions

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Fjerdingen (talk | contribs)
Overview: remove the "syntactic sugar" part. DISTINCT makes full sense, (As in many cases you can achieve the same result in many ways. Here using UNION, GROUP BY and others.)
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ISO [[SQL:2008]] introduced the <code>FETCH FIRST</code> clause.
 
According to PostgreSQL v.9 documentation, an '''SQL Windowwindow function''' ''"performs a calculation across a set of table rows that are somehow related to the current row''", in a way similar to aggregate functions.<ref>[https://www.postgresql.org/docs/9.1/static/tutorial-window.html PostgreSQL 9.1.24 Documentation - Chapter 3. Advanced Features]</ref>
The name recalls signal processing [[window function | window functions]]. A window function call always contains an '''OVER''' clause.
 
=== ROW_NUMBER() window function ===