Creating a row change timestamp column
Every time a row is added or changed in a table with a row change timestamp column, the row change timestamp column value is set to the timestamp corresponding to the time of the insert or update operation.
The data type of a row change timestamp column must be TIMESTAMP. You can define only one row change timestamp column in a table.
When you create a table, you can define a column in the table to be a row change timestamp column. For example, create a table ORDERS with columns called ORDERNO, SHIPPED_TO, ORDER_DATE, STATUS, and CHANGE_TS. Define CHANGE_TS as a row change timestamp column.
CREATE TABLE ORDERS
(ORDERNO SMALLINT,
SHIPPED_TO VARCHAR(36),
ORDER_DATE DATE,
STATUS CHAR(1),
CHANGE_TS TIMESTAMP FOR EACH ROW ON UPDATE AS ROW CHANGE TIMESTAMP NOT NULL)
When a row is inserted into the ORDERS table, the CHANGE_TS column for the row is set to the timestamp of the insert operation. Any time a row in ORDERS is updated, the CHANGE_TS column for the row is modified to reflect the timestamp of the update operation.
You can drop the row change timestamp attribute from a column:
ALTER TABLE ORDER
ALTER COLUMN CHANGE_TS
DROP ROW CHANGE TIMESTAMP
The column CHANGE_TS remains as a TIMESTAMP column in the table, but the system no longer automatically updates timestamp values for this column.