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Overview
Comment:More documentation updates. (CVS 951)
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 24b9b569240d2108b17420d85cafdc718c67269f
User & Date: drh 2003-05-03 19:04:04.000
Context
2003-05-04
07:02
new section for keywords, more docs for attached databases , links, cleanup (CVS 952) (check-in: 87e1b6a936 user: jplyon tags: trunk)
2003-05-03
19:04
More documentation updates. (CVS 951) (check-in: 24b9b56924 user: drh tags: trunk)
04:55
- added entry for ATTACH DATABASE. - added entry for DETACH DATABASE. - added soundex() function. - added some new TEMP modifiers. - added new VACUUM behavior. - added the Oracle8 outer join "(+)" syntax. - documented the modulus/remainder operator %. - added ALL as alternative to DISTINCT in SELECT. - fixed assignment list in UPDATE to use * metacharacter. - fixed value in PRAGMA to be optional. - added link from INSERT topic to REPLACE. - added optional CONSTRAINT <name> before column constraints. - skip 2 lines before each Section in the TCL source. (CVS 950) (check-in: fd28c5229e user: jplyon tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to www/faq.tcl. 
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#
# Run this script to generated a faq.html output file
#
set rcsid {$Id: faq.tcl,v 1.21 2002/11/06 14:08:12 drh Exp $}

puts {<html>
<head>
  <title>SQLite Frequently Asked Questions</title>
</head>
<body bgcolor="white">
<h1 align="center">Frequently Asked Questions</h1>




|








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#
# Run this script to generated a faq.html output file
#
set rcsid {$Id: faq.tcl,v 1.22 2003/05/03 19:04:04 drh Exp $}

puts {<html>
<head>
  <title>SQLite Frequently Asked Questions</title>
</head>
<body bgcolor="white">
<h1 align="center">Frequently Asked Questions</h1>
︙︙
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DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;
</pre></blockquote>
}



























# End of questions and answers.
#############

puts {<DL COMPACT>}
for {set i 1} {$i<$cnt} {incr i} {
  puts "  <DT><A HREF=\"#q$i\">($i)</A></DT>"








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DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;
</pre></blockquote>
}

faq {
  I deleted a lot of data but the database file did not get any
  smaller.  Is this a bug?
} {
  <p>No.  When you delete information from an SQLite database, the
  unused disk space is added to an internal "free-list" and is reused
  the next time you insert data.  The disk space is not lost.  But
  neither is it returned to the operating system.</p>

  <p>If you delete a lot of data and want to shrink the database file,
  run the VACUUM command (version 2.8.1 and later).  VACUUM will reconstruct
  the database from scratch.  This will leave the database with an empty
  free-list and a file that is minimal in size.  Note, however, that the
  VACUUM can take some time to run (around a half second per megabyte
  on the Linux box where SQLite is developed) and it can use up to twice
  as much temporary disk space as the original file while it is running.
  </p>
}

faq {
  Can I use SQLite in my commerical product without paying royalties?
} {
  <p>Yes.  SQLite is in the public domain.  No claim of ownership is made
  to any part of the code.  You can do anything you want with it.</p>
}

# End of questions and answers.
#############

puts {<DL COMPACT>}
for {set i 1} {$i<$cnt} {incr i} {
  puts "  <DT><A HREF=\"#q$i\">($i)</A></DT>"
︙︙
Changes to www/lang.tcl. 
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#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.51 2003/05/03 04:55:19 jplyon Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>




|








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#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.52 2003/05/03 19:04:04 drh Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>
︙︙
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right of the decimal point.  If the <i>Y</i> argument is omitted, 0 is 
assumed.</td>
</tr>

<tr>
<td valign="top" align="right">soundex(<i>X</i>)</td>
<td valign="top">Compute the soundex encoding of the string <i>X</i>.





This returns "?000" for a NULL argument.




</tr>

<tr>
<td valign="top" align="right">substr(<i>X</i>,<i>Y</i>,<i>Z</i>)</td>
<td valign="top">Return a substring of input string <i>X</i> that begins
with the <i>Y</i>-th character and which is <i>Z</i> characters long.
The left-most character of <i>X</i> is number 1.  If <i>Y</i> is negative








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right of the decimal point.  If the <i>Y</i> argument is omitted, 0 is 
assumed.</td>
</tr>

<tr>
<td valign="top" align="right">soundex(<i>X</i>)</td>
<td valign="top">Compute the soundex encoding of the string <i>X</i>.
The string "?000" is returned if the argument is NULL.
This function is omitted from SQLite by default.
It is only available the -DSQLITE_SOUNDEX=1 compiler option
is used when SQLite is built.</td>
</tr>

<tr>
<td valign="top" align="right">sqlite_version(*)</td>
<td valign="top">Return the version string for the SQLite library
that is running.  Example:  "2.8.0"</td>
</tr>

<tr>
<td valign="top" align="right">substr(<i>X</i>,<i>Y</i>,<i>Z</i>)</td>
<td valign="top">Return a substring of input string <i>X</i> that begins
with the <i>Y</i>-th character and which is <i>Z</i> characters long.
The left-most character of <i>X</i> is number 1.  If <i>Y</i> is negative
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<dd><p>When a constraint violation occurs, the one row that contains
the constraint violation is not inserted or changed.  But the command
continues executing normally.  Other rows before and after the row that
contained the constraint violation continue to be inserted or updated
normally.  No error is returned.</p></dd>

<dt><b>REPLACE</b></dt>
<dd><p>When a UNIQUE constraint violation occurs, the pre-existing row
that is causing the constraint violation is removed prior to inserting
or updating the current row.  Thus the insert or update always occurs.
The command continues executing normally.  No error is returned.</p>
<p>If a NOT NULL constraint violation occurs, the NULL value is replaced
by the default value for that column.  If the column has no default
value, then the ABORT algorithm is used.</p>





</dd>
</dl>

<p>
The conflict resolution algorithm can be specified in three places,
in order from lowest to highest precedence:
</p>








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<dd><p>When a constraint violation occurs, the one row that contains
the constraint violation is not inserted or changed.  But the command
continues executing normally.  Other rows before and after the row that
contained the constraint violation continue to be inserted or updated
normally.  No error is returned.</p></dd>

<dt><b>REPLACE</b></dt>
<dd><p>When a UNIQUE constraint violation occurs, the pre-existing rows
that are causing the constraint violation are removed prior to inserting
or updating the current row.  Thus the insert or update always occurs.
The command continues executing normally.  No error is returned.
If a NOT NULL constraint violation occurs, the NULL value is replaced
by the default value for that column.  If the column has no default
value, then the ABORT algorithm is used.</p>

<p>When this conflict resolution strategy delete rows in order to
statisfy a constraint, it does not invoke delete triggers on those
rows.  But that may change in a future release.</p>

</dd>
</dl>

<p>
The conflict resolution algorithm can be specified in three places,
in order from lowest to highest precedence:
</p>
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<p>The VACUUM command is an SQLite extension modelled after a similar
command found in PostgreSQL.  If VACUUM is invoked with the name of a
table or index then it is suppose to clean up the named table or index.
In version 1.0 of SQLite, the VACUUM command would invoke 
<b>gdbm_reorganize()</b> to clean up the backend database file.</p>

<p>

This command was readded after version 2.8.0. of SQLite.  It now cleans
the database by copying its contents to a temporary database file, and 
reloading the database file from it.  This will eliminate free pages, 
align table data to be contiguous, and otherwise clean up the database 
file structure.</p>

<p>This command will fail if there is an active transaction.  This 
command has no effect on an in-memory database.</p>
}


puts {
<p><hr /></p>
<p><a href="index.html"><img src="/goback.jpg" border=0 />
Back to the SQLite Home Page</a>
</p>

</body></html>}














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<p>The VACUUM command is an SQLite extension modelled after a similar
command found in PostgreSQL.  If VACUUM is invoked with the name of a
table or index then it is suppose to clean up the named table or index.
In version 1.0 of SQLite, the VACUUM command would invoke 
<b>gdbm_reorganize()</b> to clean up the backend database file.</p>

<p>
VACUUM became a no-op for version 2.0.0 of SQLite. 
The command was reactivated with version 2.8.1.  It now cleans
the database by copying its contents to a temporary database file, and 
reloading the database file from it.  This will eliminate free pages, 
align table data to be contiguous, and otherwise clean up the database 
file structure.  The index or table name argument is now ignored.</p>

<p>This command will fail if there is an active transaction.  This 
command has no effect on an in-memory database.</p>
}


puts {
<p><hr /></p>
<p><a href="index.html"><img src="/goback.jpg" border=0 />
Back to the SQLite Home Page</a>
</p>

</body></html>}