Deciding between an artificial primary key and a natural key for a ...
2009年2月26日 · You'll likely create a unique key on the natural key anyway, so making it the PK of a standalone table should be fine. One benefit is the NK is more intuitive than a surrogate …
Difference Between Natural Key and Surrogate Key? - Databases ...
2013年6月27日 · A single-column PK is usually also known as a Surrogate key, which is merely a PK column that uses a generated number that is unique in the table. A Primary Key can be …
Oracle中唯一约束和唯一索引，PK,FK,UK.CK - CSDN博客
2014年12月10日 · oracle 10g/11g学习目标：掌握表空间及用户的创建、修改和删除操作，了解oracle的基本知识，熟练掌握记录的插入、删除、修改和查询操作，了解pk/ck/uk/fk等知识， …
A New Understanding of Keys Part 2: Kinds of Keys
2018年4月22日 · A NK is a CK that arises from the conceptual model of the enterprise and represents a name or a property, either of which may be composite; A SK is artificially created …
复混肥料 - 百度百科
可以通过化学合成和混配制成，包括二元型（如NP、NK、PK）和三元型（NPK）。 这类肥料可节约包装和运输成本，减少施肥次数，也可根据当地土壤养分供应状况和目标作物需肥特性设计 …
SQL Developer Data Modeler Functionality for PK, FK, NK, and …
2016年4月12日 · How can oracle show relationships between tables & identify the true primary keys without having the additional foreign keys in other/said tables. e.g. Product Number, …
Calculate $\\sum_{k=0}^n k \\binom{n}{k} p^k (1-p)^{n-k}$
Let X1, …,Xn X 1, …, X n be independent random variables, each equal to 1 1 with probability p p and to 0 0 with probability 1 − p 1 − p. The probability that exactly k k of them are equal to 1 1 …
PTA 7-2 国际贸易统计 - 代码先锋网
输入第一行给出一个正整数N（≤104），即参与国际贸易的国家数量，则这些国家从1到N编号。 随后N行，第i行给出编号为i的国家在贸易中卖出商品的记录，格式如下：kN1 P1 ⋯Nk Pk ， …
Patryk Nowak (@nk_pk) • Instagram profile
9,518 Followers, 1,203 Following, 1,427 Posts - Patryk Nowak (@nk_pk) on Instagram: "📍Katowice MA: @xmanagement_warsaw 🏊🏼♂️former swimmer"
塿土区长期施肥农田土壤的可持续性评价 - plantnutrifert.org
ck、n、nk和pk的可持续性指数分别为0.49、0.54、0.74和0.99,均低于可持续性指数临界值1.30,其中ck和n差异不显著;np和npk处理的可持续性指数分别为1.18和1.26,两者差异不显著,接近于可 …
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