由于域可以相同为了加以区分必须对每列起一个名字称为属性Attribute。候选码若关系中的某一属性组的值能唯一地标识一个元组则称该属性组为候选码Candidatekey若一个关系有多个候选码则选定其中一个为主码Primarykey。外部码设F是基本关系R的一个或一组属性但不是关系R的码如果F与基本关系S的主码Ks相对应则称F是基本关系R的外部码Fo
It must hash the keys from the tuple according to each attribute’s SQL type, it needs to find the spot in the hash-table data structure where the tuple belongs, memory must be allocated for storing the tuple, and, finally values must be moved into the allocated spot. Additionally, the ...
calibre, version 3.40.1错误: 未处理的异常: AttributeError:'tuple' object has no attribute 'format'calibre 3.40.1 [64bit] embedded-python: True is64bit: TrueWindows-7-6.1.7601-SP1 Windows ('64bit', 'WindowsPE')('Windows', '7', '6.1.7601')Python 2.7.15+Windows: ('7', '6.1.7601'...
each attribute’s value has to be unique. This is indicated as data types that include real numbers, standard data type integers, Booleans and characters
AllfaketuplesinT2whosecolumnBvalueis2mustbeinthejoinresult providedtheysatisfyallotherpredicatesinthequery Similarhintscanbeobtainedfromresulttuplesforcase2andcase3 Insummary wecanusethevalueofjoinattributesintheresultofajointoauditthejoinquery Next weformalizeouranalysis anddevelopanef cientalgorithmtoauditjoin...