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全部博文(191)
发布时间:2024-10-29 17:28:15
overlap重叠查找算法:
一般用子查询实现,如果用join会导致结果集重复数量增多,因为不是1对1关系,而是1行对应多行。
使用子查询自关联,比如主表a,子查询的a取个别名b,对应的有start_date,end_date以及唯一标识id以及自关联的比如这里是staff_id
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发布时间:2024-10-18 10:09:58
对于表T,有object_id,按照where object_id =:oid查询,如果传入的oid是NULL,则查询全部( 希望走全表扫描 ),相当于FROM t WHERE 1=1,如果object_id传入非NULL值( 希望走索引扫描 ),则执行查询FROM t WHERE object_id =:oid,这是常见的根据传入的值不同,执行不同条件查询的语句。......【阅读全文】
吻的感觉适2025-07-18 23:11
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