Table Alias posing problem in Update statements

Hi experts,

I am facing a problem using a Alias on a table while updating that table.

I am trying something like

UPDATE Table1 T1 SET = (SELECT DISTINCT col2 FROM Table2 T2 WHERE
T2.col3 = T1.col1)

T1 and T2 are table aliases.

Here I am trying to update a column in all the rows in table "Table1"
depending on value of another column for the same row.
But the query is not working. It is not allowing alias in the update
query (i.e. alias T1 on table "Table1").

Am I making a mistake somewhere in the syntax? Or, is it just not
supported in postgresql?
I am using postgreSQL version 8.2.

I have observed similar problems with delete statements also.
But these types of queries run successfully on Oracle.

Thanks in advance.
Pushker Chaubey

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