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Remove outer join simulation using UNION now that we have had outer

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joins for quite a long time.
This commit is contained in:
Bruce Momjian 2005-02-01 02:35:48 +00:00
parent 2de7ebe910
commit 3c16965995
2 changed files with 4 additions and 33 deletions
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16
doc/FAQ
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@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL Frequently Asked Questions (FAQ) for PostgreSQL
Last updated: Mon Jan 31 21:31:39 EST 2005 Last updated: Mon Jan 31 21:35:15 EST 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@ -781,7 +781,7 @@
4.16) How do I create a column that will default to the current time? 4.16) How do I create a column that will default to the current time?
Use CURRENT_TIMESTAMP: Use CURRENT_TIMESTAMP:
CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP ); CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
4.17) How do I perform an outer join? 4.17) How do I perform an outer join?
@ -801,18 +801,6 @@
is assumed in LEFT, RIGHT, and FULL joins. Ordinary joins are called is assumed in LEFT, RIGHT, and FULL joins. Ordinary joins are called
INNER joins. INNER joins.
In previous releases, outer joins can be simulated using UNION and NOT
IN. For example, when joining tab1 and tab2, the following query does
an outer join of the two tables:
SELECT tab1.col1, tab2.col2
FROM tab1, tab2
WHERE tab1.col1 = tab2.col1
UNION ALL
SELECT tab1.col1, NULL
FROM tab1
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
ORDER BY col1
4.18) How do I perform queries using multiple databases? 4.18) How do I perform queries using multiple databases?
There is no way to query a database other than the current one. There is no way to query a database other than the current one.

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doc/src/FAQ/FAQ.html
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alink="#0000ff"> alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
<P>Last updated: Mon Jan 31 21:31:39 EST 2005</P> <P>Last updated: Mon Jan 31 21:35:15 EST 2005</P>
<P>Current maintainer: Bruce Momjian (<A href= <P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>) "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)
@ -1006,7 +1006,7 @@ length</TD></TR>
<P>Use <I>CURRENT_TIMESTAMP</I>:</P> <P>Use <I>CURRENT_TIMESTAMP</I>:</P>
<PRE> <PRE>
CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP ); CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
</PRE> </PRE>
<H4><A name="4.17">4.17</A>) How do I perform an outer join?</H4> <H4><A name="4.17">4.17</A>) How do I perform an outer join?</H4>
@ -1032,23 +1032,6 @@ length</TD></TR>
<SMALL>RIGHT</SMALL>, and <SMALL>FULL</SMALL> joins. Ordinary joins <SMALL>RIGHT</SMALL>, and <SMALL>FULL</SMALL> joins. Ordinary joins
are called <SMALL>INNER</SMALL> joins.</P> are called <SMALL>INNER</SMALL> joins.</P>
<P>In previous releases, outer joins can be simulated using
<SMALL>UNION</SMALL> and <SMALL>NOT IN</SMALL>. For example, when
joining <I>tab1</I> and <I>tab2</I>, the following query does an
<I>outer</I> join of the two tables:<BR>
<BR>
</P>
<PRE>
SELECT tab1.col1, tab2.col2
FROM tab1, tab2
WHERE tab1.col1 = tab2.col1
UNION ALL
SELECT tab1.col1, NULL
FROM tab1
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
ORDER BY col1
</PRE>
<H4><A name="4.18">4.18</A>) How do I perform queries using <H4><A name="4.18">4.18</A>) How do I perform queries using
multiple databases?</H4> multiple databases?</H4>