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Comment:Document the fact that SQLite allows NULL values in PRIMARY KEY columns and the fact that we might design to change this in the future. Ticket #518. (CVS 3373)
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SHA1: b99d845ef4776595022c6fb855e582cfe6ef2f9f
User & Date: drh 2006-08-29 13:08:38
Context
2006-08-29
18:46
Bug fix: Get INSERT INTO ... SELECT working when the target is a virtual table. (CVS 3374) check-in: 79124857 user: drh tags: trunk
13:08
Document the fact that SQLite allows NULL values in PRIMARY KEY columns and the fact that we might design to change this in the future. Ticket #518. (CVS 3373) check-in: b99d845e user: drh tags: trunk
12:04
Improved built-in help in the command-line shell. Enable the fulltext search extension in the TCL interface. (CVS 3372) check-in: 9763b4bf user: drh tags: trunk
Changes
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Changes to www/lang.tcl.

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#
# Run this Tcl script to generate the lang-*.html files.
#
set rcsid {$Id: lang.tcl,v 1.115 2006/08/16 22:58:50 drh Exp $}
source common.tcl

if {[llength $argv]>0} {
  set outputdir [lindex $argv 0]
} else {
  set outputdir ""
}
................................................................................
special names "<b>ROWID</b>", "<b>OID</b>", or "<b>_ROWID_</b>".
This is true regardless of whether or not there is an INTEGER
PRIMARY KEY.  An INTEGER PRIMARY KEY column man also include the
keyword AUTOINCREMENT.  The AUTOINCREMENT keyword modified the way
that B-Tree keys are automatically generated.  Additional detail
on automatic B-Tree key generation is available
<a href="autoinc.html">separately</a>.</p>













<p>If the "TEMP" or "TEMPORARY" keyword occurs in between "CREATE"
and "TABLE" then the table that is created is only visible
within that same database connection
and is automatically deleted when
the database connection is closed.  Any indices created on a temporary table
are also temporary.  Temporary tables and indices are stored in a



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#
# Run this Tcl script to generate the lang-*.html files.
#
set rcsid {$Id: lang.tcl,v 1.116 2006/08/29 13:08:38 drh Exp $}
source common.tcl

if {[llength $argv]>0} {
  set outputdir [lindex $argv 0]
} else {
  set outputdir ""
}
................................................................................
special names "<b>ROWID</b>", "<b>OID</b>", or "<b>_ROWID_</b>".
This is true regardless of whether or not there is an INTEGER
PRIMARY KEY.  An INTEGER PRIMARY KEY column man also include the
keyword AUTOINCREMENT.  The AUTOINCREMENT keyword modified the way
that B-Tree keys are automatically generated.  Additional detail
on automatic B-Tree key generation is available
<a href="autoinc.html">separately</a>.</p>

<p>According to the SQL standard, PRIMARY KEY should imply NOT NULL.
Unfortunately, due to a long-standing coding oversight, this is not 
the case in SQLite.  SQLite allows NULL values
in a PRIMARY KEY column.  We could change SQLite to conform to the
standard (and we might do so in the future), but by the time the
oversight was discovered, SQLite was in such wide use that we feared
breaking legacy code if we fixed the problem.  So for now we have
chosen to contain allowing NULLs in PRIMARY KEY columns.
Developers should be aware, however, that we may change SQLite to
conform to the SQL standard in future and should design new programs
accordingly.</p>

<p>If the "TEMP" or "TEMPORARY" keyword occurs in between "CREATE"
and "TABLE" then the table that is created is only visible
within that same database connection
and is automatically deleted when
the database connection is closed.  Any indices created on a temporary table
are also temporary.  Temporary tables and indices are stored in a