Physical Diagrams

A physical data diagram provides a graphical view of your database structure, and helps you analyze its tables (including their columns, indexes, and triggers), views, and procedures, and the references between them.

In the following example, the Employee table is shown in relation to the Team, Division, Material, Task, and Project tables:

• Physical Diagram Objects
  PowerDesigner supports all the objects necessary to build physical diagrams.
• Tables (PDM)
  A table is used to store data in a set of columns. Each record in the table is represented as a row, which is uniquely identified by the values in its primary key column or columns.
• Columns (PDM)
  A column is a set of values of a single type in a table. Each row of the table contains one instance of each column. Each table must have at least one column, which must have a name and code and to which you can assign a data type, either directly, or via a domain.
• Primary, Alternate, and Foreign Keys (PDM)
  A key is a column, or a combination of columns, that uniquely identifies a row in a table. Each key can generate a unique index or a unique constraint in a target database.
• Indexes (PDM)
  An index is a data structure associated with one or more columns ordered by the column values. Indexes are typically created for columns that you are frequently searched on to improve response times. Most types of index are more effective when applied to columns with high cardinality.
• Views (PDM)
  A view is a query that provides access to all or a subset of the data in a table or multiple tables connected by joins. Views do not copy the data from their underlying tables and are updated when data in those tables changes. Views can reference other views, can order or filter data as necessary, and may be indistinguishable from tables for users accessing them.
• Triggers (PDM)
  A trigger is a segment of SQL code associated with a table or a view, which is invoked automatically whenever there is an attempt to modify data in the associated table or view with an insert, delete, or update command. A DBMS trigger is not associated with any table or view, and fires on modifications to the database structure itself, such as the creation or dropping of a table or events like startup, shutdown, login etc. You can use triggers to enforce referential integrity (where declarative constraints are not sufficient) and to implement sequences for columns.
• Stored Procedures and Functions (PDM)
  You can define stored procedures and functions for any DBMS that supports them.
• Users, Groups, and Roles (PDM)
  A user is a database object that identifies a person who can login or connect to the database. Groups and roles are used to simplify the granting of rights to users, as privileges and permissions granted to a group or role are inherited by users who belong to that group or incarnate that role.
• Synonyms (PDM)
  Synonyms are alternative names for various types of database object, which can be used to mask the name and owner of the object, provide location transparency for remote objects of a distributed database, and simplify SQL statements for database users.
• Defaults (PDM)
  Default objects are named values that can be assigned to columns or domains. Defaults are available for selection from the Default list on the Check Parameters tab of column and domain property sheets. Defaults are not supported by all DBMSs.
• Domains (CDM/LDM/PDM)
  Domains allow you to group together a data type, length, precision, mandatoriness, check parameters, and business rules to standardize their application to a set of columns and entity attributes. You can define domains for columns of type ID, name, address, or any other kind of data whose use you want to standarize across multiples columns or attributes in your model.
• Sequences (PDM)
  Sequences are auto-incremented columns that allow you to define complex incrementations. Sequences are available for selection from the Sequence list on the General tab of column property sheets. Sequences are not supported by all DBMSs.
• Abstract Data Types (PDM)
  An abstract data type (ADT) is a user-defined data type which can encapsulate a data set and functions that can be performed on the data. Abstract data types are not supported by all DBMSs.
• References (PDM)
  A reference is a link between a parent table and a child table, which defines a referential integrity constraint between column pairs for a primary or alternate key and a foreign key, or between user-specified columns. Each column pair is linked by a join, and each reference can contain one or more joins. Each value in the child table column is equal to the value in the parent table column.
• View References (PDM)
  A view reference is a link between a parent table or view and a child table or view, which defines the joins between the parent and child columns. View references are not generated to the database
• Business Rules (CDM/LDM/PDM)
  A business rule can represent a government-imposed law, a customer requirement, or an internal guideline. They may start as simple observations, such as "customers call toll-free numbers to place orders", and develop into more detailed expressions during the design process such as what information a customer supplies when placing an order or how much a customer can spend based on a credit limit.
• Lifecycles (PDM)
  A lifecycle allows you to model the movement of data from expensive, rapid storage, through various forms of cheaper slower storage as the data ages and access requirements diminish. The period during which data remain in each kind of storage are modeled as phases, which are associated with tablespaces.
• Tablespaces and Storages (PDM)
  Tablespaces and storages are generic objects used to represent physical locations (in named partitions) of tables and indexes in a database or storage device.
• Web Services (PDM)
  Web services are applications stored on web servers that are accessed through standard web protocols (HTTP, SOAP) and data formats (HTML, XML...), whatever the systems and programming languages. PowerDesigner supports modeling for both the SOAP protocol, in which queries are encapsulated into services, and HTTP, where operations are invoked directly.