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Overview
| Comment: | Additional clarification on syntax restrictions in SELECT statements. |
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4c5d78209a5b03a04c805cca2db21d50 |
| User & Date: | drh 2014-01-30 15:32:07.112 |
Context
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2014-01-30
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| 15:56 | Update the mmap documentation to describe the problem of Windows not truncating memory mapped files. (check-in: fa77748670 user: drh tags: trunk) | |
| 15:32 | Additional clarification on syntax restrictions in SELECT statements. (check-in: 4c5d78209a user: drh tags: trunk) | |
| 15:03 | Further enhancements to the SELECT documentation. (check-in: 979599b0b6 user: drh tags: trunk) | |
Changes
Changes to pages/lang.in.
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3617 3618 3619 3620 3621 3622 3623 | any changes to the database. <p>The "[select-stmt]" syntax diagram above attempts to show as much of the SELECT statement syntax as possible in a single diagram, as some readers find that helpful. Alternative syntax diagrams that break the syntax down into smaller chunks are shown elsewhere in this document. | | | > | | | | > > > > | | 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 |
any changes to the database.
<p>The "[select-stmt]" syntax diagram above attempts to show as much of the
SELECT statement syntax as possible in a single diagram, as some readers
find that helpful. Alternative syntax diagrams that break the syntax down
into smaller chunks are shown elsewhere in this document.
<p>Note that there are paths through the syntax diagrams that
are not allowed in practice. Some example:
<ul>
<li>An [ORDER BY] or [LIMIT] clause can only occur on the right-most
SELECT of a [compound select].
<li>A [VALUES] clause can be the first element in a [compound SELECT]
that uses a [WITH] clause, but a [simple SELECT] that consists of
just a [VALUES] clause cannot be preceded by a [WITH] clause.
<li>The [WITH] clause must occur on the first SELECT of a [compound SELECT].
It cannot follow a [compound-operator].
</ul>
These and other similar syntax restrictions are described in the text.
<p>The SELECT statement is the most complicated command in the SQL language.
To make the description easier to follow, some of the passages below describe
the way the data returned by a SELECT statement is determined as a series of
steps. It is important to keep in mind that this is purely illustrative -
in practice neither SQLite nor any other SQL engine is required to follow
this or any other specific process.
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4099 4100 4101 4102 4103 4104 4105 | </ul> <h3>The WITH Clause</h3> <p>SELECT statements may be optional preceded by a single [WITH clause] that defines one or more [common table expressions] | | > > | 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 |
</ul>
<h3>The WITH Clause</h3>
<p>SELECT statements may be optional preceded by a single
[WITH clause] that defines one or more [common table expressions]
for use within the SELECT statement. Contrary to what the
[select-stmt] syntax diagram shows, a [WITH clause] cannot occur
after a [compound-operator].
<tcl>
##############################################################################
Section UPDATE update {UPDATE *UPDATEs}
RecursiveBubbleDiagram update-stmt
</tcl>
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