ALTER SEQUENCE

`ALTER SEQUENCE`

Sets the next value of a sequence, or changes its increment

Available in

DSQL

Syntax

ALTER {SEQUENCE | GENERATOR} seq_name
  [RESTART [WITH newvalue]]
  [INCREMENT [BY] increment]

Table 1. `ALTER SEQUENCE` Statement Parameters
Parameter	Description
seq_name	Sequence (generator) name
newvalue	New sequence (generator) value.A 64-bit integer from -2^-63 to 2⁶³-1.
increment	Increment of the sequence (when using `NEXT VALUE FOR seq_name`);cannot be `0`.

The ALTER SEQUENCE statement sets the current value of a sequence to the specified valueand/or changes the increment of the sequence.

The RESTART WITH newvalue clause allows you to set the next value generated by NEXT VALUE FOR seq_name.To achieve this, the current value of the sequence is set to (newvalue - increment) with increment either as specified in the statement, or stored in the metadata of the sequence.The RESTART clause (without WITH) restarts the sequence with the initial value stored in the metadata of the sequence.

Note

Contrary to Firebird 3.0, since Firebird 4.0 RESTART WITH newvalue only restarts the sequence with the specified value, and does not store newvalue as the new initial value of the sequence.A subsequent ALTER SEQUENCE RESTART will use the initial value specified when the sequence was created, and not the newvalue of this statement.This behaviour is specified in the SQL standard.

It is currently not possible to change the initial value stored in the metadata.

Warning

Incorrect use of the ALTER SEQUENCE statement (changing the current value of the sequence or generator) is likely to break the logical integrity of data, or result in primary key or unique constraint violations.

INCREMENT [BY] allows you to change the sequence increment for the NEXT VALUE FOR expression.

Note

Changing the increment value takes effect for all queries that run after the transaction commits.Procedures that are called for the first time after changing the commit, will use the new value if they use NEXT VALUE FOR.Procedures that were already used (and cached in the metadata cache) will continue to use the old increment.You may need to close all connections to the database for the metadata cache to clear, and the new increment to be used.Procedures using NEXT VALUE FOR do not need to be recompiled to see the new increment.Procedures using GEN_ID(gen, expression) are not affected when the increment is changed.

Who Can Alter a Sequence?

The ALTER SEQUENCE (ALTER GENERATOR) statement can be executed by:

Administrators
The owner of the sequence
Users with the ALTER ANY SEQUENCE (ALTER ANY GENERATOR) privilege