Insert data into table with result from another select query
If table_2 is empty, then try the following insert statement:
insert into table_2 (itemid,location1)
select itemid,quantity from table_1 where locationid=1
If table_2 already contains the itemid values, then try this update statement:
update table_2 set location1=
(select quantity from table_1 where locationid=1 and table_1.itemid = table_2.itemid)