oracle 使用leading, use_nl, rownum调优例子
select /*+ leading(e) use_nl(sc) */ count(sc.pmnum) into v_count from equipment e, sal_controledpnsnrange sc where (sc.new_min_item_no <= e.itemnum) and (sc.new_max_item_no >= e.itemnum) and (sc.new_min_serial_no <= e.serialnum) and (sc.new_max_serial_no >= e.serialnum) and e.itemnum = a_item_no and rownum = 1;

?执行时间大约为4秒。

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转自：http://blog.chinaunix.net/uid-574845-id-2734102.html