GATE CSE
First time here? Checkout the FAQ!
x
0 votes
535 views
R(ABC)     S(BDE)

F:A->B      B ->C     B->D     D->E

AND R HAS 100 TUPLES AND S HAS 200
asked in Databases by (143 points)   | 535 views

3 Answers

+3 votes
For R A  is key and B is key for S.B is foreign key of R refering B of S.If referential integrity is taken into consideration max and min no of tuples will be 100  and 0 (null values)if not considered max will be 100 and min will be 0(no value of B in R matches  B of S)
answered by Veteran (31.1k points)  
edited by
making it tough- what about cross product? :)
For cross product max 100*200 rows

But if referential integrity is taken how null are allowed as b is key I think min will be one 

By allowing all duplicates in R of b 

But null can also come. Even with referential integrity, child table can have null value for the referred attribute. Here, B can be null for all 100 tuples in R (this also means C is also null for all 100 tuples).

A similar question but "self-join" makes this highly complex:

http://gateoverflow.in/11698/join

Sir please give me a pen and paper explaintion if null values are allowed then it is no more referring as fkey
In referential integrity child value can be either null or a value from the parent.

For referential integrity to hold in a relational database, any field in a table that is declared a foreign key can contain either a null value, or only values from a parent table's primary key or a candidate key. In other words, when a foreign key value is used it must reference a valid, existing primary key in the parent table.

 

 

 

@sreshta, no value of B in R matches B of S. it happens when B in R has all null values right???
+1 vote
In R(ABC) and relation S(BDE) we take care on solution we find that A is candiate key for R and B is foreign key for S then apply natural join we get max 100 records because all 200 values of S surly contain 100 records of R therefore maximum value will be 100 but min u can think no match as zero value.
answered by Active (2.2k points)  
0 votes
minmun 0 and maximum 100 tuple .may be no one tuple can be match then give 0 and if match all tuples then get 100.
answered by Active (2.2k points)  

Related questions

0 votes
3 answers
1
+2 votes
0 answers
2
asked in Databases by Null&Void Active (1.9k points)   | 204 views
+3 votes
1 answer
3
asked in Databases by KISHALAY DAS Boss (6.5k points)   | 498 views


Top Users May 2017
  1. akash.dinkar12

    3548 Points

  2. pawan kumarln

    2126 Points

  3. Bikram

    1922 Points

  4. sh!va

    1682 Points

  5. Arjun

    1622 Points

  6. Devshree Dubey

    1272 Points

  7. Debashish Deka

    1270 Points

  8. Angkit

    1056 Points

  9. LeenSharma

    1028 Points

  10. Arnab Bhadra

    812 Points

Monthly Topper: Rs. 500 gift card
Top Users 2017 May 22 - 28
  1. Bikram

    1008 Points

  2. pawan kumarln

    752 Points

  3. Arnab Bhadra

    726 Points

  4. akash.dinkar12

    428 Points

  5. Arjun

    350 Points


22,896 questions
29,206 answers
65,329 comments
27,708 users