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Add support for the TOTAL() aggregate function - works like SUM() except

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that it returns 0 instead of NULL when presented with an empty list. (CVS 2930)

FossilOrigin-Name: a7f528ff3446d50b280fb0b85063879e3ac5751a
This commit is contained in:
drh
2006-01-12 22:17:50 +00:00
parent 0e6082eb83
commit a97fdd3bfc
5 changed files with 39 additions and 19 deletions
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16
www/lang.tcl
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@@ -1,7 +1,7 @@
#
# Run this Tcl script to generate the lang-*.html files.
#
set rcsid {$Id: lang.tcl,v 1.104 2006/01/04 15:58:29 drh Exp $}
set rcsid {$Id: lang.tcl,v 1.105 2006/01/12 22:17:50 drh Exp $}
source common.tcl
if {[llength $argv]>0} {
@@ -1395,15 +1395,15 @@ if all values in the group are NULL.</td>
</tr>
<tr>
<td valign="top" align="right">sum(<i>X</i>)</td>
<td valign="top" align="right">sum(<i>X</i>)<br>total(<i>X</i>)</td>
<td valign="top">Return the numeric sum of all numeric values in the group.
If there are no input rows or all values are NULL, then NULL is returned.
If there are no input rows or all values are NULL, then sum() returns
NULL but total() returns zero.
NULL is not a helpful result in that case (the correct answer should be
zero) but it is what the SQL standard requires and how
most other SQL database engines operate so SQLite does it that way
in order to be compatible.
You will probably want to use
"<b>coalesce(sum(</b>X<b>),0)</b>" instead of just "<b>sum(</b>X<b>)</b>"
zero) but the SQL standard requires that behavior from sum() and that is how
most other SQL database engines implement sum() so SQLite does it that way
in order to be compatible. The non-standard total() function is provided
as a convenient way
to work around this design problem in the SQL language.</td>
</tr>
</table>