On 8/15/23 08:04, Russell Rose | Passfield Data Systems wrote:
Hi there
I am trying to convert a SQL Anywhere database to postgres. Within SQL
anywhere a field can have a default value of ‘last user’. This means
that when you perform an update on a table, if the field is not
explicitly set then the current user is used. So for instance if I have
a field called mod_user in a table, but when I do an update on the table
and do not set mod_user then SQL Anywhere sets the field to current_uer.
I have tried to replicate this using a postgres trigger in the before
update. However, if I do not set the value then it automatically picks
up the value that was already in the field. Is there a way to tell the
difference between me setting the value to the same as the previous
value and postgres automatically picking it up.
Not that I know of. In Postgres an UPDATE is essentially a DELETE of the
OLD tuple and an INSERT of a new tuple. You cannot determine whether the
same value in a given field for the OLD/NEW records was explicitly set
the same or just carried over.
If the field myfield contains the word ‘me’. Can I tell the difference
between:
Update table1 set field1=’something’,myfield=’me’
And
Update table1 set field1=’something’
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
