How many items shipped by REG AIR were ordered on March 22, 1995?
items shipped by REG AIR refer to l_linenumber where l_shipmode = 'REG AIR'; ordered on March 22, 1995 refers to o_orderdate = '1995-03-22';
SELECT COUNT(T1.o_orderkey) FROM orders AS T1 INNER JOIN lineitem AS T2 ON T1.o_orderkey = T2.l_orderkey WHERE T2.l_shipmode = 'REG AIR' AND T1.o_orderdate = '1995-03-22'