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LessThan
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Data Mapping > Data Mapper Functions > By Category > Comparator > LessThan

Glossary Item Box

Function Name
Less Than
Category
Comparator
Icon
Less Than
Description
Determine whether one value is less than another
Inputs
Value 1 Value that must be less than Value 2 for a true output
Value 2 Value to check Value 1 against
Outputs
Result Boolean indicator - true if Value 1 is less than Value 2, false otherwise
Properties
None -

Usage

The Data Mapper Comparator Less Than function allows you to determine whether one value is less than another. The values in question may be from the input data source or components within the Mapper, such as Constants or function outputs. Since the Less Than function outputs a boolean value, it is most usefully used in conjunction with other functions such as Set and Logic components. To apply the Comparator Less Than function, use the following process:

Create a new Data Mapper file, dragging your XML data source and targets into the editor area. For this example we are using staff_source.xsd, an XML Schema Definition inferred from the following source:

Source XML Copy Code
<staff>
 <employee>
  <first_name>Mark</first_name>
  <second_name>Brown</second_name>
  <started>2001</started>
  <permanent>true</permanent>
 </employee>
 <employee>
  <first_name>Jane</first_name>
  <second_name>Jackson</second_name>
  <started>1998</started>
  <permanent>true</permanent>
 </employee>
 <employee>
  <first_name>Joe</first_name>
  <second_name>Simpson</second_name>
  <started>2008</started>
  <permanent>false</permanent>
 </employee>
 <employee>
  <first_name>Lynn</first_name>
  <second_name>Nicolson</second_name>
  <started>2008</started>
  <permanent>false</permanent>
 </employee>
</staff>

For our target schema we will be using staff_target.xsd, inferred from the following XML:

Target XML Copy Code
<company>
 <staff_member since="2000" contract="false">
  <f_name>Ken</f_name>
  <s_name>Jones</s_name>
 </staff_member>
 <staff_member since="2003" contract="true">
  <f_name>Linda</f_name>
  <s_name>Lee</s_name>
 </staff_member>
 <staff_member since="1998" contract="false">
  <f_name>Paul</f_name>
  <s_name>Mitchell</s_name>
 </staff_member>
</company>

The data models employees within an organisation. Let's assume that, rather than mapping all data values, we only want to map "employee" elements representing staff members with surnames within the first half of the alphabet - whose "second_name" values run from "A" to "M". Here is the Data Mapper with Source and Target imported:

Data Mapper Source and Target

Drag the Comparator Less Than function from the Component Palette into the mapping area:

Comparator Less Than Component

Less Than Added

The Less Than function takes two inputs representing the values you want to compare. The function output will indicate true if Value 1 is less than Value 2, and false if it is not (including if the values are equal). Both inputs and output of the Less Than function may be connected to items in the XML Reader/ Writer or other components in the Mapper.

Since we want to map only elements whose "second_name" value comes from the first half of the alphabet, connect its output in the XML Reader to the Value 1 input in the Less Than function.

Reader to Less Than

Now we need to define the value to compare the input surname to. Drag a Constant Value from the Data Type section onto the Mapper. Right-click it and choose Show Properties. Enter a String as the Data Type and "N" as the value.

Constant Properties

Connect the Constant output to the Value 2 input in the Less Than function.

Constant to Less Than

Now each time the Mapper encounters the "second_name" element, it will check whether the name is before "N" in the alphabet. If a name is less than "N", the function will output a value of true, otherwise it will output a value of false.

Let's now use this information to filter our data. Drag a Filter function from the Set section onto the Mapper. Connect its Bool input to the output of the Less Than function and its Nodes input to the "employee" output in the XML Reader.

Filter Added

Now connect the output of the Filter function to the "staff_member" input in the XML Writer. This will ensure that an "employee" element is only mapped if its "second_name" element comes from the first half of the alphabet.

Filter to Writer

Finally let's make the remaining input and output connections. Remember to map "second_name" to "s_name" - although we have used this value from the source we have not yet instructed the Mapper to map it.

Inputs and Outputs Connected

We can now execute the transform by pressing Shift-F5 or the Execute button (Execute). The transform is applied and the file we selected as output opens in the editor:

Output XML Copy Code
<company>
 <staff_member since="2001" contract="true">
  <f_name>Mark</f_name>
  <s_name>Brown</s_name>
 </staff_member>
 <staff_member since="1998" contract="true">
  <f_name>Jane</f_name>
  <s_name>Jackson</s_name>
 </staff_member>
</company>

The output only contains those "staff_member" elements with surnames from "A" to "M". Most of the Comparator functions are particularly useful when you need to filter or transform your data depending on an unknown range of input values.

The Less Than function can handle various different data types including numbers and Strings.
The Less Than function will return false if Value 1 and Value 2 are equal. The Less Than or Equal function will return true if the Values are equal.

See Also