Sequences

A sequence (also called a “generator” in Firebird) is a stored variable containing a shared value for different tables and data. Sequences generally serve to implement the current auto-increment values in databases tables. To show the “Sequences” management dialog box, select “Project | Sequences”.
Note that sequences are not supported by all the RDBMSs compatible with ERBuilder Data Modeler. For example, MySQL does not support sequences, whereas Firebird does.

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Creating a new sequence

To create a new sequence:

1. Select in the “Sequences” management dialog box.



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2. Specify the sequence caption (and eventually its name) and necessary parameters according to the used RDBMS then click to save the added sequence.
   The following table gives a brief explanation for the possible sequence characteristics:
   
   

   Sequence characteristics	Type	Possible values	Description
   Seed	Integer	An integer	The start value of the sequence
   Increment	Integer	An integer	The step value of the sequence
   Maximum value	Integer	An integer	The upper limit for the possible sequence values
   Minimal value	Integer	An integer	The lower limit for the possible sequence values
   Cycle	Enumerate	“Cycle”, “No Cycle”	Specifies if the sequence comes back to the lower limit value after reaching the upper limit value
   Cache	Enumerate	“Cache”, “No Cache”	Specifies if the RDBMS is going to store a limited number of the next sequence values in cache for quicker access (cache size must not be null)
   Integer type	Enumerate	“TINYINT”, “SMALLINT”, “INT”, “BIGINT”, “DECIMAL”, “NUMERIC”	Specify the sequence type
   Order	Enumerate	“Order”, “No Order”	Specify if the RDBMS is going to generate the sequence values in natural order (useful in a Real-time Application Cluster)