Last (query directive) - Revision history

Olli: /* Examples */

2009-08-25T10:02:31Z

‎Examples

Olli: /* Examples */

2009-08-25T08:20:59Z

‎Examples

Olli at 08:11, 25 August 2009

2009-08-25T08:11:39Z

New page

== Description ==

Returns the last or the last N rows of specified directive. May return less than specified number of rows if the inner directive does not return that many rows.

== Constructor ==

Last(Directive directive) - Returns the last row of directive.

Last(int count, Directive directive) - Returns the last ''count'' rows of directive

== Examples ==

Following example gets the sum of number of instances of instances in the input topic. The ''Count'' selects the number of instances of each instance topic. The ''Eval'' calculates the sum. It always returns sum up to the current row. Then the ''Last'' directive selects only the last row which contains the final sum.

importPackage(org.wandora.query2);
new Last(
new Eval(
"vars=dir.get(\"vars\");"+
"if(vars==null){vars={sum:0};dir.set(\"vars\",vars);}"+
"vars.sum+=parseInt(val);"+
"vars.sum;"
).as("#sum")
.from(
new Count(
new Instances()
).from(new Instances())
)
)

[[Category: Query directives]]

@@ Line 11: / Line 11: @@
 == Examples ==
-Following example gets the sum of number of instances of instances in the input topic. The ''Count'' selects the number of instances of each instance topic. The ''Eval'' calculates the sum. It always returns sum up to the current row. Then the ''Last'' directive selects only the last row which contains the final sum.
+Following example gets the sum of number of instances of instances in the input topic. The ''Count'' selects the number of instances of each instance topic. The ''Eval'' calculates the sum. It always returns sum up to the current row. Then the ''Last'' directive selects only the last row which contains the final sum. Note that it is easier to do the same thing using [[Sum (query directive) |Sum]] directive.
   importPackage(org.wandora.query2);

@@ Line 16: / Line 16: @@
   new Last(
     new Eval(
-      "vars=dir.get(\"vars\");"+
+      "param.sum+=parseInt(val);"+
-     "if(vars==null){vars={sum:0};dir.set(\"vars\",vars);}"+
+      "param.sum;"
-     "vars.sum+=parseInt(val);"+
+    ,{sum:0}).as("#sum")
-      "vars.sum;"
     ).as("#sum")
     .from(
       new Count(
@@ Line 27: / Line 25: @@
+    )
+  )
 [[Category: Query directives]]