OpenEdge Development:<br />Programming Interfaces Referencing tables and fields

Release 10.1A: OpenEdge Development:
Programming Interfaces

Referencing tables and fields

Unique table and field names do not require fully qualified references within application procedures. In a single database OpenEdge application, references to non-unique field names require a table prefix to avoid ambiguous field references. Use the following syntax to reference a non-unique field in a procedure:
Syntax
table-name.field-name 
The table–name is the name of the database table that contains the field field–name.

The ability to connect to several databases from a single OpenEdge session introduces the possibility of non-unique table names and increases the possibility of non-unique field names. References to non-unique table names within multi-database OpenEdge applications require database prefixes to avoid ambiguous table references. Ambiguous table and field references cause compilation failures.

Use the following syntax to include a database prefix in a table or field reference:
Syntax
database-name.table-name 
database-name.table-name.field-name 
The database–name is the logical name (or an alias for a logical name) that represents the database that contains the table table–name.

For example, suppose you are connected to two databases db1 and db2, both of which contain a table called customer. The following procedure will not compile due to an ambiguous table reference:
FOR EACH customer: /* In db1 or db2 ? */ 
  DISPLAY name. 
END. 
The procedure below uses fully qualified table references to display customer names from both connected databases (db1 and db2):
FOR EACH db1.customer: 
  DISPLAY name. 
END. 
FOR EACH db2.customer: 
  DISPLAY name. 
END. 
Notice that the two references to the name field do not need to be qualified because they appear within a FOR EACH block that already contain fully qualified table references.
Note: When Progress encounters a statement such as DISPLAY X.Y, it first attempts to process X.Y as a databasename.table–name. If that fails, Progress then attempts to process X.Y as table–name.field–name.