How many tables are required to implement the scenario expressed in the ERD shown below?

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My try:

  • Table (CR2) with the columns {B1, C1, C2}
  • Table (R1) with the columns {A1, P, B1}
  • Table (A) with the columns {A1, A2, A3}
  • Table (R3) with the columns {A1, B1, Q}
  • Table (B) with the columns {B1, B2}

Have I got it right? Am I missing something?

1 Answer 1


Your answer is mostly correct, except Q is a dependent attribute of R3, not a table on its own.

  • 1
    Why is C not a table of its own? Jan 29, 2017 at 19:24
  • @ypercubeᵀᴹ C is a weak entity set, R2 is an identifying relationship. C must be implemented as (B1, C1, C2) where (B1, C1) identifies the weak entity set. The relationship (B1, (B1, C1)) is derivable from that, it would be redundant to represent it as a separate table.
    – reaanb
    Jan 29, 2017 at 19:40

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