Release 10.1A: OpenEdge Data Management:
DataServer for ORACLE

Sequence generator

A sequence generator is a database object that provides incremental values within any integer range. You can specify any positive or negative increment. The DataServer supports the ORACLE sequence generator. To define ORACLE sequences, you use the SQL CREATE SEQUENCE statement and indicate the name, minimum and maximum values, increment, and whether numbers are reused. For example, this is the code for creating a sequence named seq-table-name that starts with 1 and increments by 1:

CREATE SEQUENCE seq-table-name START WITH 1 INCREMENT BY 1

Note: Do not define ORACLE sequences with names ending in _SEQ unless this manual instructs you to do so. The DataServer uses ORACLE sequences whose names end in _SEQ for internal purposes.

Table 2–3 compares the features of the OpenEdge and ORACLE sequence generators. An application that relies on sequence generators can access an OpenEdge database and, through the DataServer, an ORACLE database. See the chapter on database access in OpenEdge Development: Progress 4GL Handbook for information on defining and using OpenEdge sequences in your database applications.

Table 2–3: OpenEdge and ORACLE sequence generators 

Characteristic	OpenEdge	ORACLE
Maximum/minimum range.	Yes	Yes
Ascending/descending.	Yes	Yes
Adjustable incrementation.	Yes	Yes
Database object.	Yes	Yes
Loses a number when a record creation fails.	Yes	Yes
Sequence is disrupted during dumping or loading.	No	Yes

If you add a sequence to a table in your supporting ORACLE database, you must update the schema image to reflect this addition. See Chapter 7, "The Data Server Tutorial," for instructions on updating a schema image.

There are two Progress 4GL functions that provide information about database sequences, NEXT-VALUE and CURRENT-VALUE. When you use the DataServer, you can use these functions to get information about sequences in your ORACLE database, but you must use the NEXT-VALUE function first in the same session you use the CURRENT-VALUE function.