INSERT, UPDATE

Somebody could show me how to INSERT new rows from tab2 to tab1 and UPDATE rows of tab1 with new values from tab2

Every day I replace values in tab2 with sql-loader (REPLACE option) ( tab2 is my "temporary table" )

structure of tab1 and tab 2 are identical :

ch1 VARCHAR2(5)
ch2 VARCHAR2(5)
ch3 VARCHAR2(10)
ch4 VARCHAR2(3)

the primary key is (ch1, ch2, ch3, ch4)

i'd like to insert new rows into tab1 and i'd like to update rows with new values

to INSERT i found :

INSERT INTO tab1 ( ch1, ch2, ch3, ch4 )

	SELECT ch1, ch2, ch3, ch4 FROM  tab2
	WHERE NOT EXISTS(  
		SELECT ch1, ch2, ch3, ch4 FROM tab1
		WHERE t1.ch1 = t2.ch1
		AND t1.ch2 = t2.ch2
		AND t1.ch3 = t2.ch3
		AND t1.ch4 = t2.ch4 );

But to UPDATE i don't known well ... thanks to help me

 Jean-Yves LE STRAT
 mailto:jylestrat_at_comx.fr