Documentation Source Text

  hd_puts "<td valign=\"top\" align=\"right\" width=\"120\">$syntax</td>"
  hd_puts {<td valign="top">}
  if {[llength $keywords]==0} {
    regexp {[a-z_]+} $syntax name
    hd_fragment $name $name
  } else {
    eval hd_fragment $keywords
    hd_keywords $keywords
  }
  hd_resolve $desc
  hd_puts {</td></tr>}
}
</tcl>

<p>The core functions shown below are available by default. 

<title>The Tcl interface to the SQLite library</title>
<tcl>
proc METHOD {name text} {
  hd_puts "<a name=\"$name\"></a>\n<h3>The \"$name\" method</h3>\n"
  hd_resolve $text
}
</tcl>

<h2>The Tcl interface to the SQLite library</h2>

<p>The SQLite library is designed to be very easy to use from
a Tcl or Tcl/Tk script.  This document gives an overview of the Tcl

query requests 2 columns and there are 3 rows matching the query,
then the returned list will contain 6 elements.  For example:</p>

<blockquote>
<b>db1 eval {INSERT INTO t1 VALUES(1,'hello')}<br>
db1 eval {INSERT INTO t1 VALUES(2,'goodbye')}<br>
db1 eval {INSERT INTO t1 VALUES(3,'howdy!')}<br>
set x &#91;db1 eval {SELECT * FROM t1 ORDER BY a}&#93;</b>
</blockquote>

<p>The variable <b>$x</b> is set by the above code to</p>

<blockquote>
<b>1 hello 2 goodbye 3 howdy!</b>
</blockquote>

database.  This callback can do whatever is desired.  Presumably, the
callback will do some other useful work for a short while (such as service
GUI events) then return
so that the lock can be tried again.  The callback procedure should
return "0" if it wants SQLite to try again to open the database and
should return "1" if it wants SQLite to abandon the current operation.
}

##############################################################################
METHOD enable_load_extension {

<p>The extension loading mechanism of SQLite (accessed using the
[load_extension()] SQL function) is turned off by default.  This is
a security precaution.  If an application wants to make use of the
[load_extension()] function it must first turn the capability on using
this method.</p>

<p>This method takes a single boolean argument which will turn the
extension loading functionality on or off.</p>

<p>This method maps to the [sqlite3_enable_load_extension()] C/C++
interface.</p>
}

##############################################################################
METHOD exists {

<p>The "exists" method is similar to "onecolumn" and "eval" in that
it executes SQL statements.  The difference is that the "exists" method
always returns a boolean value which is TRUE if a query in the SQL
statement it executes returns one or more rows and FALSE if the SQL
returns an empty set.</p>

<p>The "exists" method is often used to test for the existance of
rows in a table.  For example:</p>

<blockquote><b>
if {&#91;db exists {SELECT 1 FROM table1 WHERE user=$user}&#93;} {<br>
&nbsp;&nbsp;&nbsp;# Processing if $user exists<br>
} else {<br>
&nbsp;&nbsp;&nbsp;# Processing if $user does not exist<br>
}
</b></blockquote>
}

<p>The "onecolumn" method works like 
"<a href="#eval">eval</a>" in that it evaluates the
SQL query statement given as its argument.  The difference is that
"onecolumn" returns a single element which is the first column of the
first row of the query result.</p>

<p>This is a convenience method.  It saves the user from having to
do a "<tt>&#91;lindex&nbsp;...&nbsp;0&#93;</tt>" on the results of an "eval"
in order to extract a single column result.</p>
}

##############################################################################
METHOD changes {

<p>The "changes" method returns an integer which is the number of rows

<p>For example, the following code implements a collating sequence called
"NOCASE" that sorts in text order without regard to case:
</p>

<blockquote><b>
proc nocase_compare {a b} {<br>
&nbsp;&nbsp;&nbsp;&nbsp;return &#91;string compare &#91;string tolower $a&#93; &#91;string tolower $b&#93;&#93;<br>
}<br>
db collate NOCASE nocase_compare<br>
</b></blockquote>
}

##############################################################################
METHOD collation_needed {