ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
Using the designated mapping, when generating a physical model ER/Studio knows if, for example, the logical CHAR
datatype should be converted into a string, C, or remain unchanged. From the datatype mappings ER/Studio also
knows the length and precision of the physical datatype. ER/Studio supports many different database platforms and
provides standard/default datatype mappings for each platform. For example, using the default mappings for Oracle
10g and 11g, ER/Studio maps FLOAT to BINARY_FLOAT, whereas for Oracle 9i a FLOAT attribute is mapped by
default to DOUBLE PRECISION. You can customize the default datatype mappings to create new mappings that
better suit your purposes.
Use the Datatype Mapping Editor to customize the datatype mapping as you move your logical models to physical
models.
1 Select Tools > Datatype Mapping Editor.
2 Display the mapping for the target platform, by choosing a mapping from the Select Mapping list.
3 Click New, enter a name for the mapping, and then click OK.
4 Make the changes as required, and then click OK.
Notes
• In the Datatype Mapping Editor, you can change the Physical Mapping values for every logical datatype.
• In the Datatype Mapping Editor, you can change the Is Default, Default Length, and Default Precision values only
if you haven’t defined a length, precision, or default for the datatype in the logical model.
• Rename a datatype by clicking Rename in the Datatype Mapping Editor.
• Customized datatype mappings are saved as .xml files in the ...\ERStudio_X.X\DatatypeMapping
directory.
• In the Generate Physical Model Wizard, the list of datatype mappings that you can choose from is limited to the
system mapping for the physical platform and any customized mappings that were based on this system
mapping.
• Mappings are stored in …\Embarcadero\ERStudio_X.X\DatatypeMapping.
Developing the Physical Model
In order to create a database, ensure you have the client software installed and are using the correct connection
strings. For more information, see Connecting to Database Sources and Targets.
If you do not have the client connection software for the platform for which you want to create a database, you can
generate a physical model from the logical model (See Generating a Physical Data Model), and then change the
database platform to the target database. You can then access the Database Wizard to create the DDL required to
create the database.
Generally, a logical data model represents business information and defines business rules, and a physical data
model represents the physical implementation of the model in a database. The physical design addresses the
technical implementation of a data model, and shows how the data is stored in the database. For example, you can
specify the datatype of each column in the table, and determine how tables will be stored in the database.
To design the most effective data model possible, focus on the logical design before developing the physical design. A
physical data modeler should have the technical-know-how to create data models from existing databases and to tune
the data models with referential integrity, alternate keys, indexes and how to match indexes to SQL code. In systems
development, the goal is to create an effective database application that can support some or all of your enterprise.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 143