changed 5 years ago  
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tags: Data Base

第一章

Select

\[\sigma_p(r) = \{t | t \in r 且 p(t)\} \]

  • 有 commutative

Project

  • 沒有 commutative

Assign

<-

\[ A ⋈_c B \to C \]

\[ A ⋈_c B = \sigma_{c}(A\times B)\]

\[ \pi_{list 2} = <A, B, C, D>\]
list 1 = <A, B, E>

Select a repo