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bmomjianbmomjian
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Remove outer join simulation using UNION now that we have had outer
joins for quite a long time.
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-33
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‎doc/FAQ

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Frequently Asked Questions (FAQ) for PostgreSQL
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Last updated: Mon Jan 31 21:31:39 EST 2005
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Last updated: Mon Jan 31 21:35:15 EST 2005
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Current maintainer: Bruce Momjian ([email protected])
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4.16) How do I create a column that will default to the current time?
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Use CURRENT_TIMESTAMP:
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CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP );
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CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
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4.17) How do I perform an outer join?
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is assumed in LEFT, RIGHT, and FULL joins. Ordinary joins are called
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INNER joins.
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In previous releases, outer joins can be simulated using UNION and NOT
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IN. For example, when joining tab1 and tab2, the following query does
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an outer join of the two tables:
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SELECT tab1.col1, tab2.col2
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FROM tab1, tab2
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WHERE tab1.col1 = tab2.col1
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UNION ALL
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SELECT tab1.col1, NULL
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FROM tab1
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WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
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ORDER BY col1
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4.18) How do I perform queries using multiple databases?
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There is no way to query a database other than the current one.

‎doc/src/FAQ/FAQ.html

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alink="#0000ff">
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<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
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<P>Last updated: Mon Jan 31 21:31:39 EST 2005</P>
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<P>Last updated: Mon Jan 31 21:35:15 EST 2005</P>
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<P>Current maintainer: Bruce Momjian (<A href=
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"mailto:[email protected]">[email protected]</A>)
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<P>Use <I>CURRENT_TIMESTAMP</I>:</P>
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<PRE>
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CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP );
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CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
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</PRE>
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<H4><A name="4.17">4.17</A>) How do I perform an outer join?</H4>
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<SMALL>RIGHT</SMALL>, and <SMALL>FULL</SMALL> joins. Ordinary joins
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are called <SMALL>INNER</SMALL> joins.</P>
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<P>In previous releases, outer joins can be simulated using
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<SMALL>UNION</SMALL> and <SMALL>NOT IN</SMALL>. For example, when
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joining <I>tab1</I> and <I>tab2</I>, the following query does an
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<I>outer</I> join of the two tables:<BR>
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<BR>
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</P>
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<PRE>
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SELECT tab1.col1, tab2.col2
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FROM tab1, tab2
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WHERE tab1.col1 = tab2.col1
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UNION ALL
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SELECT tab1.col1, NULL
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FROM tab1
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WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
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ORDER BY col1
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</PRE>
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<H4><A name="4.18">4.18</A>) How do I perform queries using
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multiple databases?</H4>
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