Commit b43f78ec authored by Pietro Abate's avatar Pietro Abate
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[r2004-07-04 22:34:41 by vbenzake] Empty log message

Original author: vbenzake
Date: 2004-07-04 22:34:41+00:00
parent c04b20ad
......@@ -241,8 +241,8 @@ Ok.
<p>Note that the corresponding semantics, as in SQL, is a multiset one
thus duplicates are not eliminated. To discard them, one has to use the <code>distinct_values</code> operator.
<p>Note that the corresponding semantics, as in SQL, is a multiset one.
Thus duplicates are not eliminated. To discard them, one has to use the <code>distinct_values</code> operator.
</p>
......@@ -260,6 +260,9 @@ from <_>[(x::<paper>_ | _ )*] in [bib],
]]>
</sample>
<p>
Note the pattern on the second line in the <code> from </code> clause. As the type of an element in <code>x</code> is <code><![CDATA[<paper>[ Author+ Title Conference File]]]></code>, we skip the tag : <code><![CDATA[<_>]]></code>, then we skip authors <code><![CDATA[_*]]> </code> until we find either Alain Frisch or Veronique Benzaken <code><![CDATA[ (<author>"Alain Frisch" | <author>"Veronique Benzaken")]]></code>, then we skip the remaining authors <code>_*</code>, we then capture the corresponding title <code><![CDATA[(t &<title>_)]]></code> and then ignore the tail of the sequence by writing <code>; _</code>
</p>
<p>
Result:
</p>
<sample><![CDATA[
......@@ -274,6 +277,12 @@ Ok.
<p>
This pure pattern form of the query yields (in general) better performance than the same one written in an XQuery-like programming style. However, the query optimiser automatically translates the latter into a pure pattern one
</p>
<p>
<b> Joins </b>
TO BE DONE
</p>
<p>
<b>A strange query: Formatted table generation</b>
</p>
......
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