MIME-Version: 1.0
In-Reply-To: <28115.1521177420@sss.pgh.pa.us>
References: <152110913499.1223.7026776990975251345@wrigleys.postgresql.org>
 <CAHE3wgiaV1YyQ6-v12R4bzmQoUc_5E3hBupKxHTzLXg2TOsh-g@mail.gmail.com>
 <28115.1521177420@sss.pgh.pa.us>
From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Sun, 18 Mar 2018 14:28:26 -0700
Message-ID: 
 <CAKFQuwayZRHgyQRrA=wYJnh6V-C3jZeumk=yfxjei=LxeBbGCA@mail.gmail.com>
Subject: Re: Synopsis of SELECT statement: UNION, INTERSECTION, EXCEPT
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Euler Taveira <euler@timbira.com.br>, dirk.lattermann@leanix.net,
	pgsql-docs@lists.postgresql.org
Content-Type: multipart/alternative; boundary="001a1147d3ea9a31c60567b68587"
Precedence: bulk

--001a1147d3ea9a31c60567b68587
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

As a first step we could do something like:

=E2=80=8Bbasic_select_statement is:
=E2=80=8B

> SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
>     [ * | expression [ [ AS ] output_name ] [, ...] ]
>     [ FROM from_item [, ...] ]
>     [ WHERE condition ]
>     [ GROUP BY grouping_element [, ...] ]
>     [ HAVING condition [, ...] ]
>     [ WINDOW window_name AS ( window_definition ) [, ...] ]
>

=E2=80=8Bfull_select_statement is basic_select_statement with the following
possible additional clauses tacked onto the end:

    [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST |
> LAST } ] [, ...] ]
>     [ LIMIT { count | ALL } ]
>     [ OFFSET start [ ROW | ROWS ] ]
>     [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
>     [ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name
> [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ]
>
> and that's still not right because ORDER BY et al can't be attached to a
> select_stmt that's the argument of a set operation, so really we'd need
> a couple of levels of nonterminals before we get down to the basic
> "SELECT expression FROM ..." part.  Nor has the use of parentheses been
> mentioned yet.
>

=E2=80=8BThen we can define the set clauses in terms of basic_select_stmt a=
nd
parentheses-surrounded full_select_stmt. The result of the set clause is
itself a type of basic_select_statement which can be made full by adding
one or more of the additional clauses, including ORDER BY.

David J.

--001a1147d3ea9a31c60567b68587
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"">As a first step we=
 could do something like:</div><div class=3D"gmail_extra"><div class=3D"gma=
il_quote"><div><br></div><div class=3D"gmail_default" style=3D"font-family:=
arial,helvetica,sans-serif">=E2=80=8Bbasic_select_statement is:</div><div c=
lass=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif">=E2=
=80=8B</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;bo=
rder-left:1px #ccc solid;padding-left:1ex">
SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]<br>
=C2=A0 =C2=A0 [ * | expression [ [ AS ] output_name ] [, ...] ]<br>
=C2=A0 =C2=A0 [ FROM from_item [, ...] ]<br>
=C2=A0 =C2=A0 [ WHERE condition ]<br>
=C2=A0 =C2=A0 [ GROUP BY grouping_element [, ...] ]<br>
=C2=A0 =C2=A0 [ HAVING condition [, ...] ]<br>
=C2=A0 =C2=A0 [ WINDOW window_name AS ( window_definition ) [, ...] ]<br></=
blockquote><div><br></div><div><div class=3D"gmail_default" style=3D"font-f=
amily:arial,helvetica,sans-serif">=E2=80=8Bfull_select_statement is basic_s=
elect_statement with the following possible additional clauses tacked onto =
the end:</div></div><div><br></div><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
=C2=A0 =C2=A0 [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS=
 { FIRST | LAST } ] [, ...] ]<br>
=C2=A0 =C2=A0 [ LIMIT { count | ALL } ]<br>
=C2=A0 =C2=A0 [ OFFSET start [ ROW | ROWS ] ]<br>
=C2=A0 =C2=A0 [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]<br>
=C2=A0 =C2=A0 [ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF tab=
le_name [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ]<br>
<br>
and that&#39;s still not right because ORDER BY et al can&#39;t be attached=
 to a<br>
select_stmt that&#39;s the argument of a set operation, so really we&#39;d =
need<br>
a couple of levels of nonterminals before we get down to the basic<br>
&quot;SELECT expression FROM ...&quot; part.=C2=A0 Nor has the use of paren=
theses been<br>
mentioned yet.<br></blockquote><div><br></div><div class=3D"gmail_default" =
style=3D"font-family:arial,helvetica,sans-serif">=E2=80=8BThen we can defin=
e the set clauses in terms of basic_select_stmt and parentheses-surrounded =
full_select_stmt. The result of the set clause is itself a type of basic_se=
lect_statement which can be made full by adding one or more of the addition=
al clauses, including ORDER BY.</div><div class=3D"gmail_default" style=3D"=
font-family:arial,helvetica,sans-serif"><br></div><div class=3D"gmail_defau=
lt" style=3D"font-family:arial,helvetica,sans-serif">David J.</div><div cla=
ss=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><br><=
/div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans=
-serif"><br></div><div class=3D"gmail_default" style=3D"font-family:arial,h=
elvetica,sans-serif"><br></div></div></div></div>

--001a1147d3ea9a31c60567b68587--