Getting Started with InfoSphere Data Architect

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130 Getting started with InfoSphere Data Architect 7.1 Reverse-engineering: The big picture We have seen how objects in the physical data model can be converted into objects in a database when you generate a DDL script that deploys them. Reverse-engineering is the opposite of this process: We convert an object in the database into an object in the physical data model. Figure 7.1 illustrates the big picture of reverse-engineering. Figure 7.1 – An overview of reverse-engineering The left side of Figure 7.1 illustrates that the process of reverse-engineering can be carried out from either a database or a DDL script. The reverse-engineering process creates a physical data model (.dbm) file in the Data Project Explorer of the workbench. This physical data model captures the information about the data objects in the database. Once you reverse-engineer to a physical data model, you can modify the data model, transform to a logical data model, or work with it as you would any other data model. Once you make changes to the physical data model, you should deploy the changes to the database. Use the compare function in the workbench to match the physical data model against the database and show the differences between the model in development and the model in production. Then, you can analyze the impact that your changes will have to an existing data model. Finally, use the workbench to merge the changes and generate a delta DDL file that can deploy the changes to the database. When you run this script on a database, you make the necessary modifications to the database object without losing any existing data. Note: Although you can reverse-engineer from a DDL script or an existing database, you have more options when you reverse-engineer from a database. Since the database stores a lot of metadata in catalog tables, IBM InfoSphere Data Architect can make good use of that metadata to better populate the physical data model.
Chapter 7 – Reverse-Engineering 131 7.2 Reverse-engineering with the workbench When you reverse-engineer a database, the workbench reads the details of the objects in the database and converts them to their equivalent representation in the physical data model. This simply means that if you reverse-engineer a schema that contains one table and one index, then the reverse-engineered physical data model will contain one schema with one table and one index. To understand what happens when you reverse-engineer from a DDL script, consider the following example: A DDL script creates a schema that contains a table and an index in the database. When you reverse-engineer from the DDL script, the workbench creates an equivalent representation of the schema, the table, and the index in the physical data model. We will see the process in more detail in the next section. 7.2.1 Reverse-engineering from DDL 7.2.1.1 Creating a sample DDL script First, let's create a sample DDL script from which to reverse-engineer. This DDL script creates the following database objects in the SAMPLE database connection: • A database, named SAMPLEUNIV • A schema, named UNIVERSITY, that belongs to the SAMPLEUNIV database • Two tables in the schema, named DEPARTMENT and STUDENT To create the sample DDL script: 1. Right-click on the SQL Scripts folder of your data design project, then select New -> SQL or XQuery Script. The New SQL or XQuery Script window opens. 2. Complete the New SQL or XQuery Script window: a. Specify the University Info System project. b. In the Name field, type SAMPLE_DDL.sql. c. Make sure that the following radio button is selected: SQL and XQuery Editor (for scripts that contain one or more SQL and XQuery statements) d. Click Finish. The Select Connection Profile window opens. 3. Select the SAMPLE database connection profile. Since you aren't deploying the script, you do not need to worry about a connection at this point. A blank SQL file is created and opens in the SQL Editor view. 4. Enter the following SQL statements to create the SAMPLEUNIV database with a UNIVERSITY schema and DEPARTMENT and STUDENT tables: CREATE DATABASE SAMPLEUNIV; CREATE SCHEMA "SAMPLEUNIV"."UNIVERSITY"; CREATE TABLE "UNIVERSITY"."STUDENT" (STUDENT_ID CHAR(10) NOT NULL,
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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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Getting Started with InfoSphere Data Architect

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