各大平台店铺的三项评分（物流、服务、商品）变化情况；
商品每日价格的变化记录；
股票的实时涨跌浮；
表：主键ID，商品编号，记录时的时间，记录时的价格，创建时间。
问题：获取每个商品每次的变化情况（涨跌幅、涨跌率）。
1、要想高效率的更新涨跌，就肯定不能是逐条数据更新，要通过自连表建立起对应关系，将每一条数据关联到上一次的价格数据。
2、由于数据库非常庞大，所以可能存在很多垃圾数据，就比如说相关的字段值为NULL或者非有效值的，这些数据要先排除掉。
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SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL; |
3、然后在获取每条数据的上一条数据，同样也要先排除掉垃圾数据。
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SELECT tmp_a.*, MAX(tmp_b.goods_date) AS last_date FROM( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_aLEFT JOIN( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_bON tmp_a.goods_code = tmp_b.goods_code AND tmp_a.goods_date > tmp_b.goods_date GROUP BY tmp_a.id; |
4、获取到上一条数据后，获取上条数据对应的商品价格。
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SELECT tmp_ab.*,tmp_c.goods_price AS last_price FROM( SELECT tmp_a.*, MAX(tmp_b.goods_date) AS last_date FROM ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_a LEFT JOIN ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_b ON tmp_a.goods_code = tmp_b.goods_code AND tmp_a.goods_date > tmp_b.goods_date GROUP BY tmp_a.id) AS tmp_ab LEFT JOIN (SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_cON tmp_ab.goods_code = tmp_c.goods_code AND tmp_c.goods_date = tmp_ab.last_date ORDER BY tmp_ab.id; |
5、获取到上条数据以及对应的价格后，开始进行计算，获取到最终的结果。
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SELECT *, (CONVERT(goods_price, DECIMAL(10,2)) - CONVERT(last_price, DECIMAL(10,2))) AS '涨跌幅', ROUND((CONVERT(goods_price, DECIMAL(10,2)) - CONVERT(last_price, DECIMAL(10,2)))/CONVERT(last_price, DECIMAL(10,2)), 2) AS '涨跌率'FROM ( SELECT tmp_ab.*,tmp_c.goods_price AS last_price FROM ( SELECT tmp_a.*, MAX(tmp_b.goods_date) AS last_date FROM ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_a LEFT JOIN ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_b ON tmp_a.goods_code = tmp_b.goods_code AND tmp_a.goods_date > tmp_b.goods_date GROUP BY tmp_a.id ) AS tmp_ab LEFT JOIN (SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_c ON tmp_ab.goods_code = tmp_c.goods_code AND tmp_c.goods_date = tmp_ab.last_date ORDER BY tmp_ab.id) AS tmp |
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-- 创建表SQLCREATE TABLE `test_goods_price_change` ( `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键ID', `goods_code` varchar(50) NOT NULL COMMENT '商品编码', `goods_date` int(11) NOT NULL COMMENT '记录时的时间', `goods_price` decimal(10,2) NOT NULL COMMENT '记录时的价格', `created_at` int(11) NOT NULL COMMENT '创建时间', PRIMARY KEY (`id`)) ENGINE=InnoDB CHARSET=utf8mb4;-- 获取涨跌浮SQLSELECT *, (CONVERT(goods_price, DECIMAL(10,2)) - CONVERT(last_price, DECIMAL(10,2))) AS '涨跌幅', ROUND((CONVERT(goods_price, DECIMAL(10,2)) - CONVERT(last_price, DECIMAL(10,2)))/CONVERT(last_price, DECIMAL(10,2)), 2) AS '涨跌率'FROM ( SELECT tmp_ab.*,tmp_c.goods_price AS last_price FROM ( SELECT tmp_a.*, MAX(tmp_b.goods_date) AS last_date FROM ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_a LEFT JOIN ( SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_b ON tmp_a.goods_code = tmp_b.goods_code AND tmp_a.goods_date > tmp_b.goods_date GROUP BY tmp_a.id ) AS tmp_ab LEFT JOIN (SELECT id,goods_code,goods_date,goods_price FROM test_goods_price_change WHERE goods_price IS NOT NULL AND goods_date IS NOT NULL ) AS tmp_c ON tmp_ab.goods_code = tmp_c.goods_code AND tmp_c.goods_date = tmp_ab.last_date ORDER BY tmp_ab.id) AS tmp |
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原文链接：https://www.cnblogs.com/laowenBlog/p/14732305.html
