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Terminology cleanup: class -> table, instance -> row, attribute -> column,

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etc.
This commit is contained in:
Peter Eisentraut
2001-01-13 23:58:55 +00:00
parent 0651a5799d
commit 027f144e39
38 changed files with 300 additions and 323 deletions
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49
doc/src/sgml/advanced.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.20 2001/01/05 06:34:15 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.21 2001/01/13 23:58:55 petere Exp $
-->
<chapter id="advanced">
@ -22,14 +22,14 @@ $Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.20 2001/01/05 06:34:15 tg
<title>Inheritance</title>
<para>
Let's create two classes. The capitals class contains
Let's create two tables. The capitals table contains
state capitals that are also cities. Naturally, the
capitals class should inherit from cities.
capitals table should inherit from cities.
<programlisting>
CREATE TABLE cities (
name text,
population float,
population real,
altitude int -- (in ft)
);
@ -38,20 +38,19 @@ CREATE TABLE capitals (
) INHERITS (cities);
</programlisting>
In this case, an instance of capitals <firstterm>inherits</firstterm> all
attributes (name, population, and altitude) from its
parent, cities. The type of the attribute name is
In this case, a row of capitals <firstterm>inherits</firstterm> all
columns (name, population, and altitude) from its
parent, cities. The type of the column name is
<type>text</type>, a native <productname>Postgres</productname>
type for variable length
ASCII strings. The type of the attribute population is
<type>float</type>, a native <productname>Postgres</productname>
type for double precision
ASCII strings. The type of the column population is
<type>real</type>, a type for single precision
floating point numbers. State capitals have an extra
attribute, state, that shows their state.
column, state, that shows their state.
In <productname>Postgres</productname>,
a class can inherit from zero or more other classes,
and a query can reference either all instances of a
class or all instances of a class plus all of its
a table can inherit from zero or more other tables,
and a query can reference either all rows of a
table or all rows of a tables plus all of its
descendants.
<note>
@ -109,7 +108,7 @@ SELECT name, altitude
<para>
Here the <quote>ONLY</quote> before cities indicates that the query should
be run over only the cities table, and not classes below cities in the
be run over only the cities table, and not tables below cities in the
inheritance hierarchy. Many of the commands that we
have already discussed -- <command>SELECT</command>,
<command>UPDATE</command> and <command>DELETE</command> --
@ -122,7 +121,7 @@ SELECT name, altitude
In previous versions of <productname>Postgres</productname>, the
default was not to get access to child tables. This was found to
be error prone and is also in violation of SQL99. Under the old
syntax, to get the sub-classes you append "*" to the table name.
syntax, to get the sub-tables you append "*" to the table name.
For example
<programlisting>
SELECT * from cities*;
@ -147,11 +146,11 @@ SET SQL_Inheritance TO OFF;
<para>
One of the tenets of the relational model is that the
attributes of a relation are atomic.
columns of a table are atomic.
<productname>Postgres</productname> does not
have this restriction; attributes can themselves contain
have this restriction; columns can themselves contain
sub-values that can be accessed from the query
language. For example, you can create attributes that
language. For example, you can create columns that
are arrays of base types.
</para>
@ -159,26 +158,26 @@ SET SQL_Inheritance TO OFF;
<title>Arrays</title>
<para>
<productname>Postgres</productname> allows attributes of an
instance to be defined
<productname>Postgres</productname> allows columns of a
row to be defined
as fixed-length or variable-length multi-dimensional
arrays. Arrays of any base type or user-defined type
can be created. To illustrate their use, we first create a
class with arrays of base types.
table with arrays of base types.
<programlisting>
CREATE TABLE SAL_EMP (
name text,
pay_by_quarter int4[],
pay_by_quarter integer[],
schedule text[][]
);
</programlisting>
</para>
<para>
The above query will create a class named SAL_EMP with
The above query will create a table named SAL_EMP with
a <firstterm>text</firstterm> string (name), a one-dimensional
array of <firstterm>int4</firstterm>
array of <firstterm>integer</firstterm>
(pay_by_quarter), which represents the employee's
salary by quarter and a two-dimensional array of
<firstterm>text</firstterm>