# Recent questions tagged joins

0 votes
0 answers 5 views
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.
0 votes
0 answers 18 views
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.
0 votes
1 answer 44 views
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)
1 vote
1 answer 12 views
Consider the following relations $A, B$ and $C:$ ... of $A\cup B$ is the same as that of $A$. $(A\cup B)\bowtie _{A.Id > 40 \vee C.Id < 15} C$ $7$ $4$ $5$ $9$
0 votes
0 answers 29 views
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? $8, 8$ $120, 8$ $960, 8$ $960, 120$
0 votes
0 answers 13 views
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.
1 vote
1 answer 24 views
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 $0$ $30400$ $38400$ $798400$
0 votes
0 answers 19 views
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))
0 votes
0 answers 11 views
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
0 votes
0 answers 15 views
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 $800000$ $40080$ $32020$ $100$
0 votes
0 answers 42 views
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 –
0 votes
0 answers 15 views
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
To see more, click for the full list of questions or popular tags.