Subset of FROM Clause

You can use a join to determine which column values to update by specifying a FROM clause. Columns from any table in the FROM clause can appear in the WHERE clause to provide values for the columns and rows to update. For example, in the following UPDATE statement, a FROM clause introduces tables to be joined in the WHERE clause:

UPDATE tab1 SET tab1.a = tab2.a FROM tab1, tab2, tab3 
   WHERE tab1.b = tab2.b AND tab2.c =tab3.c

UPDATE supports only a subset of the syntax listed in FROM Clause. You cannot include the LOCAL or the SAMPLES OF keywords if you are using Extended Parallel Server.