[英]Query Optimization in oracle
我需要从一张表中获取结果,并在 2 列上加入一个视图。
查看:800 万条记录表:5K 条记录
我浏览了查询计划并观察到查询将需要很长时间才能运行,实际上尝试运行此查询但没有得到任何结果。
请帮助我优化查询。我没有使用任何提示。
SELECT coupon_upc
, sum ( loyalty_a ) a
, sum ( loyalty_b ) b
, sum ( loyalty_c ) c
, sum ( loyalty_x )
FROM ( SELECT ccd.coupon_upc AS coupon_upc
, ( CASE WHEN a.loyalty_cell = 'A' then 1 else 0 end ) AS loyalty_a
, ( CASE WHEN a.loyalty_cell = 'B' then 1 else 0 end ) AS loyalty_b
, ( CASE WHEN a.loyalty_cell = 'C1' then 1 else 0 end ) AS loyalty_c
, ( CASE WHEN a.loyalty_cell = 'X' then 1 else 0 end ) AS loyalty_x
FROM view1 a
, ( select distinct coupon_upc
, coupon_id
, division
from table2
where schedule_key = 'XXX' ) ccd
WHERE a.campaign_code = 'XXX'
AND a.coupon_id = ccd.coupon_id
AND a.division = ccd.division ) a
GROUP BY coupon_upc
如果没有解释计划或模式/DDL,可以进行的优化是有限的。
这是一个替代方案,但您需要对其进行测试以查看它是否有任何不同。 (用相关的子查询替换连接。)
SELECT
coupon_upc, sum(loyalty_a) a, sum(loyalty_b) b, sum(loyalty_c) c, sum(loyalty_x) x
FROM
(
SELECT
(
SELECT
coupon_upc
FROM
table2
WHERE
schedule_key = 'XXX'
AND coupon_id = a.coupon_id
AND division = a.division
GROUP BY
coupon_upc
) as coupon_upc,
(case when a.loyalty_cell = 'A' then 1 else 0 end) as loyalty_a,
(case when a.loyalty_cell = 'B' then 1 else 0 end) as loyalty_b,
(case when a.loyalty_cell = 'C1' then 1 else 0 end) as loyalty_c,
(case when a.loyalty_cell = 'X' then 1 else 0 end) as loyalty_x
FROM
view1 a
WHERE
a.campaign_code = 'XXX'
) a
GROUP BY
coupon_upc
除此之外,优化的种类是:
- 坚持观点
- 索引
- 重构数据结构
编辑
查询的另一个可能的重构......我不知道 Oracle 将如何优化相关子查询的 4 个实例。
SELECT
coupon_upc,
SUM((SELECT COUNT(*) FROM view1 WHERE campaign_code = 'XXX' AND loyalty_cell = 'A' AND coupon_id = map.coupon_id AND division = map.division)) AS loyalty_a,
SUM((SELECT COUNT(*) FROM view1 WHERE campaign_code = 'XXX' AND loyalty_cell = 'B' AND coupon_id = map.coupon_id AND division = map.division)) AS loyalty_b,
SUM((SELECT COUNT(*) FROM view1 WHERE campaign_code = 'XXX' AND loyalty_cell = 'C1' AND coupon_id = map.coupon_id AND division = map.division)) AS loyalty_c,
SUM((SELECT COUNT(*) FROM view1 WHERE campaign_code = 'XXX' AND loyalty_cell = 'X' AND coupon_id = map.coupon_id AND division = map.division)) AS loyalty_x
FROM
(
SELECT coupon_upc, coupon_id, division
FROM table2 WHERE schedule_key = 'xxx'
GROUP BY coupon_upc, coupon_id, division
)
AS map
GROUP BY
coupon_upc
或者可能...
SELECT
map.coupon_upc, SUM(data.loyalty_a) AS a, SUM(data.loyalty_b) AS b, SUM(data.loyalty_c) AS c, SUM(data.loyalty_x) AS X
FROM
(
SELECT coupon_upc, coupon_id, division
FROM table2 WHERE schedule_key = 'xxx'
GROUP BY coupon_upc, coupon_id, division
)
AS map
INNER JOIN
(
SELECT
coupon_id,
division,
SUM(CASE WHEN loyalty_cell = 'A' THEN 1 ELSE 0 END) AS loyalty_a,
SUM(CASE WHEN loyalty_cell = 'B' THEN 1 ELSE 0 END) AS loyalty_b,
SUM(CASE WHEN loyalty_cell = 'C1' THEN 1 ELSE 0 END) AS loyalty_c,
SUM(CASE WHEN loyalty_cell = 'X' THEN 1 ELSE 0 END) AS loyalty_x
FROM
view1
WHERE
campaign_code = 'XXX'
)
AS data
ON data.coupon_id = map.coupon_id
AND data.division = map.division
GROUP BY
map.coupon_upc
另一种可能的重写是:
SELECT
map.coupon_upc
, COUNT(CASE WHEN a.loyalty_cell = 'A' THEN 1 ELSE NULL END) AS loyalty_a
, COUNT(CASE WHEN a.loyalty_cell = 'B' THEN 1 ELSE NULL END) AS loyalty_b
, COUNT(CASE WHEN a.loyalty_cell = 'C1' THEN 1 ELSE NULL END) AS loyalty_c
, COUNT(CASE WHEN a.loyalty_cell = 'X' THEN 1 ELSE NULL END) AS loyalty_x
FROM
( SELECT coupon_upc, coupon_id, division
FROM table2 WHERE schedule_key = 'xxx'
GROUP BY coupon_upc, coupon_id, division
) AS map
JOIN view1 a
ON a.coupon_id = map.coupon_id
AND a.division = map.division
WHERE
a.campaign_code = 'xxx'
GROUP BY
map.coupon_upc
您对JOIN
、 WHERE
和GROUP BY
子句中使用的字段有索引吗?
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