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Implement TODO item:

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* Change LIMIT val,val to offset,limit to match MySQL

Documentation updates too.
This commit is contained in:
Bruce Momjian
2001-09-23 03:39:01 +00:00
parent ddfdb1e3f1
commit 1aab783b59
4 changed files with 22 additions and 17 deletions
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20
doc/src/sgml/ref/select.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.46 2001/09/14 10:28:09 ishii Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.47 2001/09/23 03:39:01 momjian Exp $
Postgres documentation
-->
@ -29,7 +29,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
[ { UNION | INTERSECT | EXCEPT [ ALL ] } <replaceable class="PARAMETER">select</replaceable> ]
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ FOR UPDATE [ OF <replaceable class="PARAMETER">tablename</replaceable> [, ...] ] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]]
[ LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
where <replaceable class="PARAMETER">from_item</replaceable> can be:
@ -613,7 +614,8 @@ SELECT name FROM distributors ORDER BY code;
<synopsis>
<replaceable class="PARAMETER">table_query</replaceable> UNION [ ALL ] <replaceable class="PARAMETER">table_query</replaceable>
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]]
[ LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
</synopsis>
where
@ -662,7 +664,8 @@ SELECT name FROM distributors ORDER BY code;
<synopsis>
<replaceable class="PARAMETER">table_query</replaceable> INTERSECT [ ALL ] <replaceable class="PARAMETER">table_query</replaceable>
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]]
[ LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
</synopsis>
where
@ -702,7 +705,8 @@ SELECT name FROM distributors ORDER BY code;
<synopsis>
<replaceable class="PARAMETER">table_query</replaceable> EXCEPT [ ALL ] <replaceable class="PARAMETER">table_query</replaceable>
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]]
[ LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
</synopsis>
where
@ -738,7 +742,7 @@ SELECT name FROM distributors ORDER BY code;
</title>
<para>
<synopsis>
LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]
LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL }
OFFSET <replaceable class="PARAMETER">start</replaceable>
</synopsis>
@ -761,14 +765,14 @@ SELECT name FROM distributors ORDER BY code;
constrains the result rows into a unique order. Otherwise you will get
an unpredictable subset of the query's rows---you may be asking for
the tenth through twentieth rows, but tenth through twentieth in what
ordering? You don't know what ordering, unless you specified ORDER BY.
ordering? You don't know what ordering unless you specify ORDER BY.
</para>
<para>
As of <productname>Postgres</productname> 7.0, the
query optimizer takes LIMIT into account when generating a query plan,
so you are very likely to get different plans (yielding different row
orders) depending on what you give for LIMIT and OFFSET. Thus, using
orders) depending on what you use for LIMIT and OFFSET. Thus, using
different LIMIT/OFFSET values to select different subsets of a query
result <emphasis>will give inconsistent results</emphasis> unless
you enforce a predictable result ordering with ORDER BY. This is not

5
doc/src/sgml/sql.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.21 2001/05/22 16:00:00 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.22 2001/09/23 03:39:01 momjian Exp $
-->
<chapter id="sql">
@ -864,7 +864,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
[ { UNION | INTERSECT | EXCEPT [ ALL ] } <replaceable class="PARAMETER">select</replaceable> ]
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ FOR UPDATE [ OF <replaceable class="PARAMETER">class_name</replaceable> [, ...] ] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } [ { OFFSET | , } <replaceable class="PARAMETER">start</replaceable> ]]
[ LIMIT [ <replaceable class="PARAMETER">start</replaceable> , ] { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
</synopsis>
</para>