Compare (query directive) - Revision history

Olli: /* Examples */

2009-08-21T10:03:55Z

‎Examples

Olli at 08:29, 21 August 2009

2009-08-21T08:29:54Z

Olli at 07:22, 21 August 2009

2009-08-21T07:22:38Z

Olli at 07:50, 20 August 2009

2009-08-20T07:50:18Z

New page

== Description ==

Compares the values of two roles in the input column. The directive constructor is given a comparison operator as a string. It can be one of "==", "!=", "<", ">", "<=", ">=" or various aliases of these commonly used in programming languages. It can also be one of two topic map related operators "t=" or "t!=". These compare the equality or inequality, respectively, of topics instead of numeric or string representations the values.

== Constructor ==

Compare(String role1,String comp,String role2)

Compare(String role1,String comp,String role2,boolean numeric) - If numeric is true, converts the values to numbers before comparing

== Notes ==

The where method present in every directive can be given three strings corresponding to the first constructor. A new Compare directive will be implicitly created. A.where("r1","==","r2") will resolve to new From(new Compare("r1","==","r2"),A).

[[Category:Query directives]]

← Older revision		Revision as of 10:03, 21 August 2009
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	Above example gets all instances of the input topic which have an occurrence with the value of a string literal "Test".		Above example gets all instances of the input topic which have an occurrence with the value of a string literal "Test".
		+
		+	Following example finds all topics in the topic map that have more than 5 instances. Note the use of true as fourth parameter to ''where'' to enable numeric comparison instead of textual. Also, the literal 5 must also be surrounded by quotes even though it is treated as a number.
		+
		+	importPackage(org.wandora.query2);
		+	new Count(new Instances())
		+	.as("#count")
		+	.from(new AllTopics().as("#topic"))
		+	.where("#count",">","\"5\"",true)
		+

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

← Older revision		Revision as of 08:29, 21 August 2009
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	The where method present in every directive can be given three strings corresponding to the first constructor. A new Compare directive will be implicitly created. A.where("r1","==","r2") will resolve to new From(new Compare("r1","==","r2"),A).		The where method present in every directive can be given three strings corresponding to the first constructor. A new Compare directive will be implicitly created. A.where("r1","==","r2") will resolve to new From(new Compare("r1","==","r2"),A).
		+
		+	== Examples ==
		+
		+	importPackage(org.wandora.query2);
		+	importPackage(org.wandora.topicmap);
		+	new Join(
		+	new Instances().as("#instance"),
		+	new Players(
		+	XTMPSI.SUPERCLASS_SUBCLASS,
		+	XTMPSI.SUBCLASS).whereInputIs(XTMPSI.SUPERCLASS)
		+	).where("#instance","t=",XTMPSI.SUBCLASS)
		+
		+	Above example joins instances and subclasses of input and only includes rows where the topics with roles "#instance" and XTMPSI.SUBCLASS are the same. Effectively this query finds out if any of the instances of the input topic are also subclasses of it. ''Compare'' directive is implicitly created by passing the ''where'' method string parameters corresponding to the ''Compare'' constructor.
		+
		+	importPackage(org.wandora.query2);
		+	new If(
		+	new BaseName().where("#DEFAULT","!=",null),
		+	new BaseName(),
		+	new First(new SubjectIdentifiers())
		+	)
		+
		+	Above example gets the base name of input or the first subject identifier if base name is not defined. The ''BaseName'' directive returns null when base name is not defined. The return value is compared to null to find out if it is defined.
		+
		+	importPackage(org.wandora.query2);
		+	importPackage(org.wandora.topicmap);
		+	new Occurrence("http://www.wandora.org/occurrence",XTMPSI.getLang("en"))
		+	.as("#occ")
		+	.from(new Instances())
		+	.where("#occ","=","\"Test\"")
		+
		+	Above example gets all instances of the input topic which have an occurrence with the value of a string literal "Test".

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

@@ Line 1: / Line 1: @@
 == Description ==
-Compares the values of two roles in the input column. The directive constructor is given a comparison operator as a string. It can be one of "==", "!=", "<", ">", "<=", ">=" or various aliases of these commonly used in programming languages. It can also be one of two topic map related operators "t=" or "t!=". These compare the equality or inequality, respectively, of topics instead of numeric or string representations the values.
+Compares the values of two roles in the input column.
 == Constructor ==
-Compare(String role1,String comp,String role2)
+Compare(String operand1,String operator,String operand2)
-Compare(String role1,String comp,String role2,boolean numeric) - If numeric is true, converts the values to numbers before comparing
+Compare(String operand1,String operator,String operand2,boolean numeric) - If numeric is true, converts the values to numbers before comparing
 == Notes ==