Getting Started with InfoSphere Data Architect

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152 Getting started with InfoSphere Data Architect Figure 8.9 – Viewing all of the proposed mappings 6. View the mappings and verify that they should be mapped together. In this case, you would speak with your extended team at the satellite campus to determine what each column is intended to do, and then determine which columns should be mapped. Since you reverseengineered the NEW_SDT_INFO_SYS.dbm physical data model, you know that the discovered relationships are, in fact, mapped correctly. 7. Right-click in the mapping editor and select Accept All Mappings. The color of the mapping lines changes to light-blue, making them a valid part of the mapping model. 8. Save your work. 8.3 Types of mapping Five types of mappings can be identified, depending on their properties and how they were created. Mappings are represented in the editor by lines that are drawn between the source and target nodes. Each mapping line contains a hub in the middle of the line. The color of the line depends on the type of mapping. Discovered mapping lines contain hubs that appear as brackets. All other mapping lines contain square hubs. • Mappings: A mapping connects one or more source columns to a single target column or an XML schema document (XSD) simple element or attribute. • Discovered mappings: These are the mappings proposed from the Discover Relationships wizard. You can either accept or reject the individual mapping of each relationship. Discovered mapping lines contain hubs that appear as brackets, until you approve or reject them. If you approve a discovered mapping, the hub changes to a square. • Constant mappings: These mappings have a target element, but they do not have a source element. This can be used to select a transformation function like date or time function to assign
Chapter 8 – Model Mapping and Discovery 153 it to target element. You create constant mappings by right-clicking a target element in the Mapping Group Details view, then selecting Create Constant Mapping from the menu. • Mapping groups: Mapping groups sort mapped elements by the target table (in a relational database) or by the element (in an XML schema). When you generate scripts for these mapping groups, one query is generated per mapping group. • Invalid mappings: The mapping becomes invalid when you change the properties of data objects in the source or target model. When the mapping editor is opened, all of the mappings are re-validated. If the source or target object is no longer valid, then the mapping is invalidated and a red “X” will appear on the mapping line. 8.4 Adding expressions and filters to the mapping model You can create transformation statements for each mapping that is created. The expression may be a filter, join, sort, or a transform function on a source column to get the desired target column value. The expression may change either the value or data type of the source column to be compatible with the target column. These expressions are SQL fragments and appear in the DDL that you generate from the mapping model. Let's create a mapping transformation expression to make sure that all of the rows in the STUDENT.FIRST_NAME column of the NEW_SDT_INFO_SYS.dbm physical data model appear in uppercase when they are consolidated with the information in the STUDENT_INFO_SYSTEM.dbm physical data model. To create a transformation expression: 1. Select the mapping line between the two STUDENT.FIRST_NAME columns. The properties of the mapping appear in the Properties view. 2. Click the Expression Builder button next to the Transformation field. The Expression Builder window opens. 3. Select a function. In this case, you will add a function to make sure that all first names stored in the database are stored in uppercase characters. Expand the String node and select the UCASE(VARCHAR) – VARCHAR function. The function appears in the Transformation expression pane. 4. Place the cursor between the parentheses, as shown in Figure 8.10.
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G E T T I N G S T A R T E D W I T H
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5 Notices This information was deve
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7 Trademarks IBM, the IBM logo, and
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10 Getting started with InfoSphere
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17 About the Authors Erin Wilson is
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19 Contributors The following peopl
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PART I - OVERVIEW AND SETUP 21
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Chapter 2 - Data Modeling Overview
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Chapter 2 - Data Modeling Overview
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