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有时我在表中有超过1百万行。随机化行更新
每批将有100,000个随机行。
随机化行的最佳方法是什么?
我做到以下几点:
UPDATE temp1 SET `batch` = '';
UPDATE temp1 SET `batch` = 'B1' WHERE batch = '' order by rand(number) limit 100000;
UPDATE temp1 SET `batch` = 'B2' WHERE batch = '' order by rand(number) limit 100000;
UPDATE temp1 SET `batch` = 'B3' WHERE batch = '' order by rand(number) limit 100000;
UPDATE temp1 SET `batch` = 'B4' WHERE batch = '' order by rand(number) limit 100000;
UPDATE temp1 SET `batch` = 'B5' WHERE batch = '' order by rand(number) limit 100000;
你到底想达到什么目的?为什么要随机更新? (因为最后,所有匹配的行都会被更新) –
我随机化'numbers'字段,因为当前的数字按顺序排序。一旦它被随机化,我将每个批次导出为CSV。 – user1246800