Sequences¶

A sequence is an Oracle object used to generate a number sequence. This can be useful when you need to create an autonumber column to act as a primary key.

If MigSupportSequence is set to true (default), a sequence is created in the PUBLIC schema.

Note

CACHE and ORDER cannot be migrated.
In Oracle, the maximum value of MAXVALUE can be set to 999999999999999999999999999. In GaussDB(DWS), the maximum value of MAXVALUE can be set to 9223372036854775807.
Before migrating a sequence, copy the content in the sequence_scripts.sql file and paste it to execute the script in all the target databases. For details, see Executing Custom DB Scripts.

Sequence¶

Input - CREATE SEQUENCE

CREATE SEQUENCE GROUP_DEF_SEQUENCE
  minvalue 1
  maxvalue 100000000000000000000
  start with 1152
  increment by 1
  cache 50
  order;

Output

INSERT
     INTO
          PUBLIC.MIG_SEQ_TABLE (
               SCHEMA_NAME
               ,SEQUENCE_NAME
               ,START_WITH
               ,INCREMENT_BY
               ,MIN_VALUE
               ,MAX_VALUE
               ,CYCLE_I
               ,CACHE
               ,ORDER_I
          )
     VALUES (
          UPPER( current_schema ( ) )
          ,UPPER( 'GROUP_DEF_SEQUENCE' )
          ,1152
          ,1
          ,1
          ,9223372036854775807
          ,FALSE
          ,20
          ,FALSE
     )
;

SEQUENCE with NOCACHE¶

Input - CREATE SEQUENCE with NOCACHE

CREATE SEQUENCE customers_seq
 START WITH 1000
 INCREMENT BY   1
 NOCACHE
 NOCYCLE;

Output

INSERT
     INTO
          PUBLIC.MIG_SEQ_TABLE (
               SCHEMA_NAME
               ,SEQUENCE_NAME
               ,START_WITH
               ,INCREMENT_BY
               ,MIN_VALUE
               ,MAX_VALUE
               ,CYCLE_I
               ,CACHE
               ,ORDER_I
          )
     VALUES (
          UPPER( current_schema ( ) )
          ,UPPER( 'customers_seq' )
          ,1000
          ,1
          ,1
          ,999999999999999999999999999
          ,FALSE
          ,20
          ,FALSE
     )
;

Input - CREATE SEQUENCE with a specified schema name¶

Input - CREATE SEQUENCE with a specified schema name

CREATE SEQUENCE scott.seq_customers
 START WITH 1000 INCREMENT BY 1
 MINVALUE 1000 MAXVALUE 999999999999999
 CACHE 20 CYCLE ORDER;

Output

INSERT
     INTO
          PUBLIC.MIG_SEQ_TABLE (
               SCHEMA_NAME
               ,SEQUENCE_NAME
               ,START_WITH
               ,INCREMENT_BY
               ,MIN_VALUE
               ,MAX_VALUE
               ,CYCLE_I
               ,CACHE
               ,ORDER_I
          )
     VALUES (
          UPPER( 'scott' )
          ,UPPER( 'seq_customers' )
          ,1000
          ,1
          ,1000
          ,999999999999999
          ,TRUE
          ,20
          ,FALSE
     )
;

CREATE SEQUENCE with a Default Value¶

Input - SEQUENCE with a default value

CREATE SEQUENCE seq_orders;

Output

INSERT
     INTO
          PUBLIC.MIG_SEQ_TABLE (
               SCHEMA_NAME
               ,SEQUENCE_NAME
               ,START_WITH
               ,INCREMENT_BY
               ,MIN_VALUE
               ,MAX_VALUE
               ,CYCLE_I
               ,CACHE
               ,ORDER_I
          )
     VALUES (
          UPPER( current_schema ( ) )
          ,UPPER( 'seq_orders' )
          ,1
          ,1
          ,1
          ,999999999999999999999999999
          ,FALSE
          ,20
          ,FALSE
     )
;

NEXTVAL¶

To migrate the NEXTVAL function, a custom function is provided for generating the next value based on increment_by, max_value, min_value, and cycle. During the DSC installation, this function should be created in all the databases where the migration is to be performed.

NEXTVAL supports all GaussDB(DWS) versions.

NEXTVAL is a system function of Oracle and is not implicitly supported by GaussDB(DWS). To support this function, DSC creates a NEXTVAL function in the PUBLIC schema. The PUBLIC.NEXTVAL function is used in the migrated statements.

Note

If MigSupportSequence is set to true, NEXTVAL is migrated to PUBLIC.NEXTVAL('[schema].sequence').

If MigSupportSequence is set to false, NEXTVAL is migrated to NEXTVAL('[schema].sequence').

Before migrating the NEXTVAL function, copy the content in the sequence_scripts.sql file and paste it to execute the script in all the target databases. For details, see Executing Custom DB Scripts.

Input - NEXTVAL

[schema.]sequence.NEXTVAL

Output

PUBLIC.nextval('[schema.]sequence')

Input - NEXTVAL

SELECT
          EMP_ID_SEQ.NEXTVAL INTO
               SEQ_NUM
          FROM
               dual
;

Output

SELECT
          PUBLIC.NEXTVAL ('EMP_ID_SEQ') INTO
               SEQ_NUM
          FROM
               dual
;

CURRVAL¶

To migrate the CURRVAL function, you can customize one to return the current value of a sequence. During the DSC installation, this function should be created in all the databases where the migration is to be performed.

CURRVAL is a system function of Oracle and is not implicitly supported by GaussDB(DWS). To support this function, DSC creates a CURRVAL function in the PUBLIC schema. The PUBLIC.CURRVAL function is used in the migrated statements.

Note

If MigSupportSequence is set to true, CURRVAL is migrated to PUBLIC.CURRVAL('[schema].sequence').

If MigSupportSequence is set to false, CURRVAL is migrated to CURRVAL('[schema].sequence').

Input - CURRVAL

[schema.]sequence.CURRVAL

Output

currval('[schema.]sequence')

Input - CURRVAL

INSERT
     INTO
          Line_items_tab (
               Orderno
               ,Partno
               ,Quantity
          )
     VALUES (
          Order_seq.CURRVAL
          ,20321
          ,3
     )
;

Output

INSERT
     INTO
          Line_items_tab (
               Orderno
               ,Partno
               ,Quantity
          ) SELECT
                    PUBLIC.CURRVAL ('Order_seq')
                    ,20321
                    ,3
;

last updated: 2024-11-13 15:46 UTC - commit: bdcb01d62e4f1de672b662d88ef6cb8eb3a27a29