Minimum relations

Question

Comments

Answer given is 5. Please anyone can explain this.

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3 is directly shown in above figure

2 more tables are for R1 and R2(since they are m:n relationships)

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3 were not given directly. I uploaded the solution image in the comment. .

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i also said seeing that uploaded image, by directly i mean, you can directly find out :)

see,

for (1:1 and total participation at atleast one side, you can merge 2 tables) , as done for (E1 E4) and (E2 E3)

weak entity always have a seperate table (E5)

(m:n) relationship will also need seperate table, as for (R1) and (R2)

remaining relationships are shown by foreign keys, so no extra table,

so total tables required at minimum are (E1 E4), (E2 E3), (E5), (R1) and (R2) = 5