Managing Generation and Reverse Engineering

PowerDesigner supports reverse engineering and generation through both scripts and live database connections.

In this section:

Statement is used to define a piece of SQL syntax. Statements often contain variables that will be evaluated during generation and script reverse engineering.
Query is reserved for describing live database reverse engineering

Statements for script generation, script reverse engineering, and live database generation are identical, whereas live database reverse engineering may require specific queries.

The processes of generation and reverse-engineering can be defined as follows:

Generation - statements are parsed and variables are evaluated and replaced by their actual values taken from the current model. The same statements are used for script and live database generation.
Reverse engineering – may be performed by:
- Script - PowerDesigner parses the script and identifies the different statements thanks to the terminator (defined in Script\Sql\Syntax). Each individual statement is "associated" with an existing statement in the DBMS definition file in order to commit the variables in the reversed statement as items in a PowerDesigner model.
- Live database connection - special queries are used to retrieve information from the database system tables. Each column of a query result set is associated with a variable. The query header specifies the association between the columns of the resultset and the variable. The values of the returned records are stored in these variables which are then committed as object attributes.

For more information on variables, see Optional strings and variables.

Script Category
The Script category contains the following kinds of items:
ODBC Category
The ODBC category contains items for live database generation when the DBMS does not support the generation statements defined in the Script category.
Script Generation
Script generation statements are available in the Script category, under the different object categories. For example, in Sybase ASA 8, the Create statement in the Table category is the following:
Script Reverse Engineering
The same statements are used for generation and reverse engineering.
Live Database Generation
In general, live database generation uses the same statements as script generation. However, when the DBMS does not support standard SQL syntax, special generation statements are defined in the ODBC category. This is the case for MSACCESS that needs VB scripts to create database objects during live database generation.
Live Database Reverse Engineering
The DBMS contains live database reverse engineering queries for retrieving objects (like Table, Columns, and so on) from the database.
Generating and Reverse Engineering Extended Objects
Some DBMSs have objects that cannot be represented by the standard PowerDesigner model objects. However, you can work with these objects, generate and reverse-engineer them through the use of extended objects. To do this you must first create an extended object, and then define its generation and reverse engineering scripts.
Adding Scripts Before or After Generation and Reverse Engineering
You can specify scripts to be used before or after database generation or reverse engineering.

Parent topic: DBMS Definition Files