0.1 对多和 1对多有什么区别么？解决思路

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0..1 对多和 1对多有什么区别么？
1对多或者多对1 我懂，
但有时候看到有0..1这样的0对多或者1对多，就不明白了
为什么还有一个0掺和进来呢？

14 years, 2 months ago

wsawsjj 14 years, 2 months ago

左外连接？哦`

answered 14 years, 2 months ago

xvzan answered 14 years, 2 months ago

0..1就是所谓的left out join

answered 14 years, 2 months ago

印度尼西亚之力 answered 14 years, 2 months ago