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单表自关联 操作
source link: https://www.oschina.net/question/4780473_2322175
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单表自关联 操作
osc_27182321 发布于 昨天 16:51
有这样一个问题 是一个单表自关联操作
select t.m_id as mId,t.box as box from tb_features t where t.m_id != #{mId} and t.index_flag = 'Y'
and t.vector_index = 1 and (select sum(t1.vector * t2.vector) from tb_features t1 left join tb_features t2 on
t1.vector_index = t2.vector_index where t1.m_id = #{mId} and t1.vector_index != 1 and t2.m_id = t.m_id) >
(t.vector * (select t3.vector from tb_features t3 where t3.m_id = #{mId} and t3.vector_index = 1) * 0.9)
vector 浮点类型 vector_index 是vector的下标 下标相等的才会相乘
几乎都需要全表扫描 mysql 的性能达不到理想效果 有什么优化的地方吗 或者换个存储方式
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