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6 votes
6 votes

Consider Table  

R1                                                              R2
actname    branch                                branch
das               tsr                                         tsr
das               tvm                                        pkd
raju               tsr
raju               pkd
radha            tsr
radha            pkd   

 R1 / R2  means   " customers who have account in all branches of bank described in R2 "

Output
raju
radha

Right ?  

What if R2 contains 0 tuples ? Will it work ? If so How ?

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1 Answer

Best answer
9 votes
9 votes
  • Assuming no foreign key constraint on attribute branch from $R1$ to $R2$

Then  Query: customers who have an account in all branches of bank described in $R2$.

O/P should be:

raju 
radha


When R2 is empty.

O/P should be all actname present in $R1$


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