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Remove FAQ mention of DROP column.

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Bruce Momjian
2005-02-01 01:41:37 +00:00
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2 changed files with 12 additions and 35 deletions
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21
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 20:35:58 EST 2005 Last updated: Mon Jan 31 20:41:21 EST 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@ -51,7 +51,7 @@
4.1) How do I SELECT only the first few rows of a query? A random row? 4.1) How do I SELECT only the first few rows of a query? A random row?
4.2) How do I find out what tables, indexes, databases, and users are 4.2) How do I find out what tables, indexes, databases, and users are
defined? How do I see the queries used by psql to display them? defined? How do I see the queries used by psql to display them?
4.3) How do you remove a column from a table, or change its data type? 4.3) How do you change a column's data type?
4.4) What is the maximum size for a row, a table, and a database? 4.4) What is the maximum size for a row, a table, and a database?
4.5) How much database disk space is required to store data from a 4.5) How much database disk space is required to store data from a
typical text file? typical text file?
@ -491,25 +491,16 @@
query to get information about the database. query to get information about the database.
There are also system tables beginning with pg_ that describe these There are also system tables beginning with pg_ that describe these
too. Use psql -l will list all databases. too.
Use psql -l will list all databases.
Also try the file pgsql/src/tutorial/syscat.source. It illustrates Also try the file pgsql/src/tutorial/syscat.source. It illustrates
many of the SELECTs needed to get information from the database system many of the SELECTs needed to get information from the database system
tables. tables.
4.3) How do you remove a column from a table, or change its data type? 4.3) How do you change a column's data type?
DROP COLUMN functionality was added in release 7.3 with ALTER TABLE
DROP COLUMN. In earlier versions, you can do this:
BEGIN;
LOCK TABLE old_table;
SELECT ... -- select all columns but the one you want to remove
INTO TABLE new_table
FROM old_table;
DROP TABLE old_table;
ALTER TABLE new_table RENAME TO old_table;
COMMIT;
Changing the data type of a column can be done easily in 8.0 and later Changing the data type of a column can be done easily in 8.0 and later
with ALTER TABLE ALTER COLUMN TYPE. with ALTER TABLE ALTER COLUMN TYPE.

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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 20:35:58 EST 2005</P> <P>Last updated: Mon Jan 31 20:41:21 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>)
@ -74,8 +74,7 @@
<A href="#4.2">4.2</A>) How do I find out what tables, indexes, <A href="#4.2">4.2</A>) How do I find out what tables, indexes,
databases, and users are defined? How do I see the queries used databases, and users are defined? How do I see the queries used
by <I>psql</I> to display them?<BR> by <I>psql</I> to display them?<BR>
<A href="#4.3">4.3</A>) How do you remove a column from a <A href="#4.3">4.3</A>) How do you change a column's data type?<BR>
table, or change its data type?<BR>
<A href="#4.4">4.4</A>) What is the maximum size for a row, a <A href="#4.4">4.4</A>) What is the maximum size for a row, a
table, and a database?<BR> table, and a database?<BR>
<A href="#4.5">4.5</A>) How much database disk space is required <A href="#4.5">4.5</A>) How much database disk space is required
@ -645,28 +644,15 @@
database.</P> database.</P>
<P>There are also system tables beginning with <I>pg_</I> that describe <P>There are also system tables beginning with <I>pg_</I> that describe
these too. Use <I>psql -l</I> will list all databases.</P> these too.</P>
<P>Use <I>psql -l</I> will list all databases.</P>
<P>Also try the file <I>pgsql/src/tutorial/syscat.source</I>. It <P>Also try the file <I>pgsql/src/tutorial/syscat.source</I>. It
illustrates many of the <SMALL>SELECT</SMALL>s needed to get illustrates many of the <SMALL>SELECT</SMALL>s needed to get
information from the database system tables.</P> information from the database system tables.</P>
<H4><A name="4.3">4.3</A>) How do you remove a column from a <H4><A name="4.3">4.3</A>) How do you change a column's data type?</H4>
table, or change its data type?</H4>
<P><SMALL>DROP COLUMN</SMALL> functionality was added in release 7.3
with <SMALL>ALTER TABLE DROP COLUMN</SMALL>. In earlier versions,
you can do this:</P>
<PRE>
BEGIN;
LOCK TABLE old_table;
SELECT ... -- select all columns but the one you want to remove
INTO TABLE new_table
FROM old_table;
DROP TABLE old_table;
ALTER TABLE new_table RENAME TO old_table;
COMMIT;
</PRE>
<P>Changing the data type of a column can be done easily in 8.0 <P>Changing the data type of a column can be done easily in 8.0
and later with <SMALL>ALTER TABLE ALTER COLUMN TYPE</SMALL>. and later with <SMALL>ALTER TABLE ALTER COLUMN TYPE</SMALL>.