Triggers

I have postgres sql 7.4
I have a table employee having two fields employee_number varchar(10) ,
salary(10,2);[primary key employee_number)

I want to track any change due update on any row on this table on this
table.

For this purpose I have created a table call emplyee_audit having the
same structure as employee but no primary key

For this purpose I have tried to use trigger with before update option.
But as could find that Post gres does not support the :old or :new clause.
So I have not able track changes in emplyee_audit.

Kindly suggest how to accomplish the above task

Regards

Anindya Bhattacharyya
Manager SI

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