From (query directive) - Revision history

Olli: /* Examples */

2009-08-20T09:40:30Z

‎Examples

Olli at 09:38, 20 August 2009

2009-08-20T09:38:25Z

Olli: /* Notes */

2009-08-20T09:36:47Z

‎Notes

Olli at 08:51, 20 August 2009

2009-08-20T08:51:34Z

Olli at 07:44, 20 August 2009

2009-08-20T07:44:13Z

Olli at 07:33, 20 August 2009

2009-08-20T07:33:48Z

New page

== Description ==

Takes the results from one directive and feeds them one row at a time to another combining all results.

== Constructor ==

From(Directive to,Directive from)

== Notes ==

This directive is best used using the from method present in every directive. Calling A.from(B) will resolve to new From(A,B).

The from method, but not the directive constructor, can be given several directives. In this case they will be joined using the Join directive. A.from(B,C) will resolve to new From(A,new Join(B,C)).

You may also give the from method, not the directive constructor, one or more strings. In this case a Literals directive will be implicitly created from the strings. A.from("b","c","d") resolves to new From(A,new Literals("b","c","d")).

← Older revision		Revision as of 09:40, 20 August 2009
Line 37:		Line 37:
	new Instances().to(new BaseName())		new Instances().to(new BaseName())

		+	One good place to use ''to'' instead of ''from'' is modifying the initial input before it gets to anything else. For example changing the role so the initial input is not overwritten immediately in other directives (see [[As (query directive) \|As]] directive).
		+
		+	importPackage(org.wandora.query2);
		+	new As("#input").to(
		+	new BaseName()
		+	)

	[[Category:Query directives]]		[[Category:Query directives]]

@@ Line 15: / Line 15: @@
 You may also give the ''from'' method, not the directive constructor, one or more strings. In this case a [[Literals (query directive) |Literals]] directive will be implicitly created from the strings. ''A.from("b","c","d")'' resolves to ''new From(A,new Literals("b","c","d"))''.
-All directives also have a ''to'' method which is inverse of ''from''. It is advisable that you use this sparingly as mixing both ''from'' and ''to'' in the same query can make it very hard to follow where the input comes from and where results go. The next two queries are equivalent.
+All directives also have a ''to'' method which is inverse of ''from''. It is advisable that you use this sparingly as mixing both ''from'' and ''to'' in the same query can make it very hard to follow where the input comes from and where results go. ''A.from(B)'' is same as ''B.to(A)''.
-−
- importPackage(org.wandora.query2);
- new BaseName().from(new Instances())
-−
- importPackage(org.wandora.query2);
- new Instances().to(new BaseName())
 == Examples ==
@@ Line 34: / Line 28: @@
 Above example gets instances of the specified topic. The from method implicitly creates a [[Literals (query directive) |Literals]] directive. [[Instances (query directive) |Instances]] directive can take as input both topics or subject identifier string so this works without explicitly converting the string to a topic.
 [[Category:Query directives]]

← Older revision		Revision as of 09:36, 20 August 2009
Line 14:		Line 14:

	You may also give the ''from'' method, not the directive constructor, one or more strings. In this case a [[Literals (query directive) \|Literals]] directive will be implicitly created from the strings. ''A.from("b","c","d")'' resolves to ''new From(A,new Literals("b","c","d"))''.		You may also give the ''from'' method, not the directive constructor, one or more strings. In this case a [[Literals (query directive) \|Literals]] directive will be implicitly created from the strings. ''A.from("b","c","d")'' resolves to ''new From(A,new Literals("b","c","d"))''.
		+
		+	All directives also have a ''to'' method which is inverse of ''from''. It is advisable that you use this sparingly as mixing both ''from'' and ''to'' in the same query can make it very hard to follow where the input comes from and where results go. The next two queries are equivalent.
		+
		+	importPackage(org.wandora.query2);
		+	new BaseName().from(new Instances())
		+
		+	importPackage(org.wandora.query2);
		+	new Instances().to(new BaseName())

	== Examples ==		== Examples ==

@@ Line 9: / Line 9: @@
 == Notes ==
-This directive is best used using the from method present in every directive. Calling A.from(B) will resolve to new From(A,B).
+This directive is best used using the from method present in every directive. Calling ''A.from(B)'' will resolve to ''new From(A,B)''.
-The from method, but not the directive constructor, can be given several directives. In this case they will be joined using the Join directive. A.from(B,C) will resolve to new From(A,new Join(B,C)).
+The ''from'' method, but not the directive constructor, can be given several directives. In this case they will be joined using the [[Join (query directive)|Join]] directive. ''A.from(B,C)'' will resolve to ''new From(A,new Join(B,C))''.
 [[Category:Query directives]]

← Older revision		Revision as of 07:44, 20 August 2009
Line 14:		Line 14:

	You may also give the from method, not the directive constructor, one or more strings. In this case a Literals directive will be implicitly created from the strings. A.from("b","c","d") resolves to new From(A,new Literals("b","c","d")).		You may also give the from method, not the directive constructor, one or more strings. In this case a Literals directive will be implicitly created from the strings. A.from("b","c","d") resolves to new From(A,new Literals("b","c","d")).
		+
		+	[[Category:Query directives]]