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ALTER SEQUENCE — change the definition of a sequence generator
ALTER SEQUENCE [schema.]sequence [ sequence_option [,... ] ]
sequence_option can be one of the following:
ALTER SEQUENCE is used to specify a new starting value of an existing sequence. Future values of the sequence will not be less than the value specified. This operation can not be rolled back and its effects are instantly visible to all other transactions.
ALTER SEQUENCE command can also change the
QUANTUM SIZE for the sequence. This is the size of the block of integer values that will be reserved for a transaction engine (TE) to be later assigned.
For details about sequence behavior, see CREATE SEQUENCE.
By default, only the user that creates a sequence database object can
ALTER the sequence. This user can
ALTER privilege on the sequence to other users (see
SELECT privilege needs to be granted to other users to
SELECT from the sequence.
Name of an existing
SEQUENCE to alter.
value is optional. It sets the new starting value for the
value must be an integer value greater than the current
ceiling value for the sequence. The starting
value must be an integer value greater than zero (0). The starting
value can also be an expression that returns an integer value. Some examples of an expression include, but are not limited to:
SELECT). This must be enclosed by parentheses. This includes all valid SQL
SELECTstatements, including statements using aggregate functions,
LIMIT, etc. The SQL
SELECTstatement must return a number value.
New size indicating the block size for the number of integer values that will be reserved for a given TE. The default value is 100.
The following example creates a sequence and creates a table that uses the new sequence to generate ID column values.
USE SCHEMA1 CREATE SEQUENCE seq_test START WITH 1; CREATE TABLE tst_table (id INTEGER GENERATED ALWAYS AS IDENTITY (seq_test), column2 STRING); INSERT INTO tst_table (column2) VALUES ('row1'),('row2'); SELECT * FROM tst_table;ID COLUMN2 --- -------- 1 row1 2 row2
SELECT NEXT VALUE FOR seq_test FROM DUAL;TST_SEQ -------- 3
INSERT INTO tst_table (column2) VALUES ('row3'),('row4'); SELECT * FROM tst_table;ID COLUMN2 --- -------- 1 row1 2 row2 4 row3 5 row4
ALTER SEQUENCE command can use the
START WITH option to change the new starting value of a sequence, but can only increase it. In the following example, the START WITH option value of one (1) is less than the current value 6. Therefore, the sequence is not altered.
ALTER SEQUENCE seq_test START WITH 1000; SELECT NEXT VALUE FOR seq_test FROM DUAL;SEQ_TEST --------- 1001
ALTER SEQUENCE command is not transactional. Its effects become visible immediately to all transactions and can't be rolled back.