A leading tool that makes Database Engineers to enter their Entity Relationship (ER) diagrams in a graphical method and generate physical database strategies for common relational database management systems such as Microsoft SQL Server and Oracle is ERwin.
| Criteria | ERwin |
| ERwin application | Data modeling |
| ERwin advantages | Simple visual interface to manage complex data |
| ERwin accessibility | Simple and user-friendly |
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ERwin supports a pattern of features of database strategy, which includes modeling the data, forward engineering (It is the process of formation of a database schema and physical database on the basis of a data model), and reverse engineering (It is the process of formation of a data model on the basis of an available database) for a wide-ranging varieties of relational DBMS, including Oracle, Microsoft Access, Sybase, DB2, and many more.
The upper portion of the workspace consists of Menu and Toolbars. The middle portion of the workspace consists of two panes: the model explorer panel and the diagram window. The lower portion contains two windows: first is the action log that shows a log of all alterations made to the data model under design, and second is the advisories panel that shows messages related to actions executed on the data model under design.
There are three model types supported by ERwin which is used by a Database Developer:
- Logical: It is a theoretical model that contains entities, attributes, and relationships. This model type is principally at the ER modeling level.
- Physical: It is a database-specific model that comprises columns, relational tables, and their associated data types.
- Logical/Physical: It is a single model that contains both theoretical-level objects and physical-level tables.
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If you want to add an entity type to the database design, either right-click on the ‘Entities’ entry in the model explorer window and select ‘New’ or select the ‘Entity’ icon in the Menus and Toolbars section of the workspace and click on the diagram window panel.
ERwin supports three types of relationships, i.e., many-to-many, identifying, and non-identifying. ERwin categorizes the child entity type in a classifying relationship as ‘weak.’ To add a relationship, in the model explorer window, right-click on the ‘Relationships’ entry and select ‘New.’ This will help in creating a new relationship.
ERwin offers a dominant feature called forward engineering that permits Database Developers to transform the ER design into a schema generation SQL script for one or more target relational databases. The resulting SQL script is obtained by choosing ‘Tools’, then ‘Forward Engineering’, and then ‘Schema-Generation’ option available in the Menus and Toolbars section and by clicking on the ‘Preview’ button.
- Supertype/Subtype Example:
ERwin supports the formation of subtype/supertype relationships among entity types. To produce design in ERwin, there are three entity types that need to be created first. After that, one has to click on the subtype button in the Menus and Toolbars section, and then click on the supertype entity in the diagram window. Once that is done, click on the subtype entity in the diagram window. This procedure may be recurrent for adding other subtypes as well.