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使用查询改写提高查询性能
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编辑：华夏媒体 作者：未知 来源：网络 时间：2006-07-29 总浏览量：5451 |
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2 HASH JOIN
3 HASH JOIN
4 VIEW
5 SORT UNIQUE
6 TABLE ACCESS FULL TIME
7 MAT_VIEW REWRITE ACCESS FULL MONTHLY_SALES_MV
8 TABLE ACCESS FULL PRODUCT
维度的ATTRIBUTE子句指明了一对一关系。例如，你可以判定从time_key开始是一周中的哪一天。假设你希望得到每年1月份的销售总额：你仍然可以使用清单 5中所示的monthly_sales_mv物化视图。注意该查询的WHERE子句如何具有一个在物化视图中没有出现的选择条件。
代码清单 5：通过joinback和ATTRIBUTE获得销售总额
SELECT t.year, p.category, SUM(ps.purchase_price) as sum_of_sales
FROM time t, product p, purchases ps
WHERE t.time_key = ps.time_key AND
ps.product_id = p.product_id AND
t.month_name = ’January’
GROUP BY t.year, p.category;
Id Operation Name
__________________________________________________
0 SELECT STATEMENT
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