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Welcome to GATE CSE Doubts, where you can ask questions and receive answers from other members of the community.

Recent questions tagged joins

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0 answers 5 views
Selfdoubt(Relational Algebra and SQL)
Is the JOIN operations(natural , left , right) in relational algebra and SQL same or is there any difference based on the condition? Please provide reference.
Is the JOIN operations(natural , left , right) in relational algebra and SQL same or is there any difference based on the condition? Please provide reference.
asked May 27 in Databases samir757 29 points 5 views
0 votes
0 answers 18 views
Joins in Relational Algebra (Self Doubt) while reading Elmasri Navathe
No. of tuples obtained as the output of an outer join (left, right or full outer join) is a superset of the no. of tuples obtained in Natural join. Is the abv. statement TRUE or FALSE? State with Reason.
asked Jan 10 in Databases shubhojit1412 5 points 18 views
0 votes
1 answer 44 views
Self Doubt (Nested Loop Join)
Can someone please clarify why we keep the smaller loop outer and the bigger loop inner? (i.e. why do we select the relation with smaller number of tuples as the outer relation)
Can someone please clarify why we keep the smaller loop outer and the bigger loop inner? (i.e. why do we select the relation with smaller number of tuples as the outer relation)
asked Aug 16, 2020 in Databases Mellophi 363 points 44 views
1 vote
1 answer 12 views
GATE2012-50 Video Solution
Consider the following relations $A, B$ and $C:$ ... is the same as that of $A$. $(A\cup B)\bowtie _{A.Id > 40 \vee C.Id < 15} C$ $7$ $4$ $5$ $9$
Consider the following relations $A, B$ and $C:$ ... of $A\cup B$ is the same as that of $A$. $(A\cup B)\bowtie _{A.Id > 40 \vee C.Id < 15} C$ $7$ $4$ $5$ $9$
asked Apr 18, 2020 in Databases admin 573 points 12 views
0 votes
0 answers 29 views
GATE2004-14 Video Solution
Consider the following relation schema pertaining to a students database: Students (rollno, name, address) Enroll (rollno, courseno, coursename) where the primary keys are shown underlined. The number of tuples in the student and Enroll tables are $120$ and $8$ respectively. What ... (Student * Enroll), where *' denotes natural join? $8, 8$ $120, 8$ $960, 8$ $960, 120$
Consider the following relation schema pertaining to a students database: Students (rollno, name, address) Enroll (rollno, courseno, coursename) where the primary keys are shown underlined. The number of tuples in the student and Enroll tables are $120$ and $8$ respectively. What are the maximum and ... in (Student * Enroll), where *' denotes natural join? $8, 8$ $120, 8$ $960, 8$ $960, 120$
asked Apr 18, 2020 in Databases admin 573 points 29 views
0 votes
0 answers 13 views
GATE2014-2-30 Video Solution
Consider a join (relation algebra) between relations $r(R)$ and $s(S)$ using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R))<size(s(S)) , the join ... $s(S)$ is more than 0.5. join selection factor between $r(R)$ and $s(S)$ is less than 0.5.
Consider a join (relation algebra) between relations $r(R)$ and $s(S)$ using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R))<size(s(S)) , the join will have fewer number of ... $r(R)$ and $s(S)$ is more than 0.5. join selection factor between $r(R)$ and $s(S)$ is less than 0.5.
asked Apr 18, 2020 in Databases admin 573 points 13 views
1 vote
1 answer 24 views
GATE2005-IT-82b Video Solution
A database table $T_1$ has $2000$ records and occupies $80$ disk blocks. Another table $T_2$ has $400$ records and occupies $20$ disk blocks. These two tables have to be joined as per a specified join condition that needs to be evaluated for ... outer loop, the reduction in number of block accesses required for reading the data will be $0$ $30400$ $38400$ $798400$
A database table $T_1$ has $2000$ records and occupies $80$ disk blocks. Another table $T_2$ has $400$ records and occupies $20$ disk blocks. These two tables have to be joined as per a specified join condition that needs to be evaluated for every pair of records ... in the outer loop, the reduction in number of block accesses required for reading the data will be $0$ $30400$ $38400$ $798400$
asked Apr 18, 2020 in Databases admin 573 points 24 views
0 votes
0 answers 19 views
GATE2007-IT-68 Video Solution
Consider the following relation schemas : b-Schema = (b-name, b-city, assets) a-Schema = (a-num, b-name, bal) d-Schema = (c-name, a-number) Let branch, account and depositor be respectively instances of the above schemas. Assume that account and ... depositor) Пc-name (σb-city = "Agra" branch ⋈ (σb-city = "Agra" ⋀ bal < 0 account ⋈ depositor))
Consider the following relation schemas : b-Schema = (b-name, b-city, assets) a-Schema = (a-num, b-name, bal) d-Schema = (c-name, a-number) Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger ... < 0 account) ⋈ depositor) Пc-name (σb-city = "Agra" branch ⋈ (σb-city = "Agra" ⋀ bal < 0 account ⋈ depositor))
asked Apr 18, 2020 in Databases admin 573 points 19 views
0 votes
0 answers 11 views
GATE2006-IT-14 Video Solution
Consider the relations r1(P, Q, R) and r2(R, S, T) with primary keys P and R respectively. The relation r1 contains 2000 tuples and r2 contains 2500 tuples. The maximum size of the join r1⋈ r2 is : 2000 2500 4500 5000
Consider the relations r1(P, Q, R) and r2(R, S, T) with primary keys P and R respectively. The relation r1 contains 2000 tuples and r2 contains 2500 tuples. The maximum size of the join r1⋈ r2 is : 2000 2500 4500 5000
asked Apr 18, 2020 in Databases admin 573 points 11 views
0 votes
0 answers 15 views
GATE2005-IT-82a Video Solution
A database table $T_1$ has $2000$ records and occupies $80$ disk blocks. Another table $T_2$ has $400$ records and occupies $20$ disk blocks. These two tables have to be joined as per a specified join condition that needs to be evaluated for every ... be used in outer loop, the number of block accesses required for reading the data are $800000$ $40080$ $32020$ $100$
A database table $T_1$ has $2000$ records and occupies $80$ disk blocks. Another table $T_2$ has $400$ records and occupies $20$ disk blocks. These two tables have to be joined as per a specified join condition that needs to be evaluated for every pair of records from ... table to be used in outer loop, the number of block accesses required for reading the data are $800000$ $40080$ $32020$ $100$
asked Apr 18, 2020 in Databases admin 573 points 15 views
0 votes
0 answers 42 views
Self Doubt - Nested Loop Join (No. of Seeks)
What do you mean by Seek? For Natural Loop Join, we calculate No. of Seeks are (nr + br). Assume that, Relation r is called the Outer Relation and Relation s is called the Inner Relation. (ni,bj) – ni represents total no. of tuples and bj represents no. of blocks in that relation. Reference (Korth) – For Block Nested-Loop Join –
What do you mean by Seek? For Natural Loop Join, we calculate No. of Seeks are (nr + br). Assume that, Relation r is called the Outer Relation and Relation s is called the Inner Relation. (ni,bj) – ni represents total no. of tuples and bj represents no. of blocks in that relation. Reference (Korth) – For Block Nested-Loop Join –
asked Sep 10, 2019 in Databases ayushsomani -1 points 42 views
0 votes
0 answers 15 views
Doubts Regarding join algorithm
What is the number of block access in Indexed Nested Loop join & Sort-merge Join??? given, No. of blocks in relation R = $B_{r}$ No. of blocks in relation S = $B_{s}$ No. of records in relation i = $r_{i}$ Join is like R x S & size of R is less than size of S
What is the number of block access in Indexed Nested Loop join & Sort-merge Join??? given, No. of blocks in relation R = $B_{r}$ No. of blocks in relation S = $B_{s}$ No. of records in relation i = $r_{i}$ Join is like R x S & size of R is less than size of S
asked Jul 10, 2019 in Databases mrinmoyh 23 points 15 views
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