2206 Update statement is ambiguous

Advantage Error Guide

The table to be updated is listed more than once in the FROM clause of an UPDATE statement. A sample ambiguous update statement is:

UPDATE table1 SET col1 = 2 FROM table1 a INNER JOIN table1 b WHERE a.id = b.id2

It is not possible for the SQL engine to determine whether the instance "a" of table1 or the instance "b" of table1 should be updated.