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Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.
I. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}
II. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}
III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}
I. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}
II. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}
III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}
- a)I and II only
- b)I and III only
- c)II and III only
- d)I, II, and III
Correct answer is option 'D'. Can you explain this answer?
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Verified Answer
Consider a database that has the relation schemas EMP (EmpId, EmpName,...
A SAFE EXPRESSION is one that is guaranteed to yield a finite number of tuples as its results. Otherwise, it is called UNSAFE Given, DepId can be permitted to be NULL
I. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))} : Gives empnames who donot belong to any department
II. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))} : Gives empnames who donot belong to some department
III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}: Gives empnames who donot belong to same department
All of these queries are giving some results which are finite and thus all are safe expressions.
Therefore, option D is correct.
I. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))} : Gives empnames who donot belong to any department
II. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))} : Gives empnames who donot belong to some department
III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}: Gives empnames who donot belong to same department
All of these queries are giving some results which are finite and thus all are safe expressions.
Therefore, option D is correct.
Most Upvoted Answer
Consider a database that has the relation schemas EMP (EmpId, EmpName,...
Understanding the given queries:
The given queries are expressed in tuple relational calculus and involve two relation schemas, EMP and DEPT. The attributes in the EMP schema are EmpId, EmpName, and DepId, while the attributes in the DEPT schema are DeptName and DeptId.
The queries involve finding tuples (t) that satisfy certain conditions. Let's analyze each query separately.
Query I:
{t | ∃u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∃v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where there exists a tuple (u) in the EMP relation such that the EmpName attribute of t is equal to the EmpName attribute of u. Similarly, there exists a tuple (v) in the DEPT relation such that the DeptId attribute of t is equal to the DeptId attribute of v.
Query II:
{t | ∀u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∃v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where for all tuples (u) in the EMP relation, the EmpName attribute of t is equal to the EmpName attribute of u. Similarly, there exists a tuple (v) in the DEPT relation such that the DeptId attribute of t is equal to the DeptId attribute of v.
Query III:
{t | ∃u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∀v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where there exists a tuple (u) in the EMP relation such that the EmpName attribute of t is equal to the EmpName attribute of u. Moreover, for all tuples (v) in the DEPT relation, the DeptId attribute of t is equal to the DeptId attribute of v.
Analyzing the answer:
To determine the correct answer option, let's consider the conditions specified in each query and how they relate to the given relation schemas.
- Query I requires that there exists a matching EmpName in EMP and a matching DeptId in DEPT for each tuple (t). This means that the tuples (t) must have a valid EmpName and DeptId combination from the respective relations.
- Query II requires that all tuples (u) in EMP have a matching EmpName in t, and there exists a matching DeptId in DEPT for each tuple (t). This means that the tuples (t) must have a valid EmpName for all tuples in EMP and a valid DeptId from DEPT.
- Query III requires that there exists a matching EmpName in EMP for each tuple (t), and all tuples (v) in DEPT have a matching DeptId in t. This means that the tuples (t) must have a valid EmpName from EMP and a valid DeptId for all tuples in DEPT.
The correct answer:
Based on the analysis, the correct answer is option 'D' (I, II, and III) as all three queries involve valid combinations of EmpName and DeptId from the EMP and DEPT relations.
The given queries are expressed in tuple relational calculus and involve two relation schemas, EMP and DEPT. The attributes in the EMP schema are EmpId, EmpName, and DepId, while the attributes in the DEPT schema are DeptName and DeptId.
The queries involve finding tuples (t) that satisfy certain conditions. Let's analyze each query separately.
Query I:
{t | ∃u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∃v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where there exists a tuple (u) in the EMP relation such that the EmpName attribute of t is equal to the EmpName attribute of u. Similarly, there exists a tuple (v) in the DEPT relation such that the DeptId attribute of t is equal to the DeptId attribute of v.
Query II:
{t | ∀u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∃v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where for all tuples (u) in the EMP relation, the EmpName attribute of t is equal to the EmpName attribute of u. Similarly, there exists a tuple (v) in the DEPT relation such that the DeptId attribute of t is equal to the DeptId attribute of v.
Query III:
{t | ∃u ∈ EMP (t[EmpName] = u[EmpName]) ∧ ∀v ∈ DEPT (t[DeptId] = v[DeptId])}
This query selects tuples (t) where there exists a tuple (u) in the EMP relation such that the EmpName attribute of t is equal to the EmpName attribute of u. Moreover, for all tuples (v) in the DEPT relation, the DeptId attribute of t is equal to the DeptId attribute of v.
Analyzing the answer:
To determine the correct answer option, let's consider the conditions specified in each query and how they relate to the given relation schemas.
- Query I requires that there exists a matching EmpName in EMP and a matching DeptId in DEPT for each tuple (t). This means that the tuples (t) must have a valid EmpName and DeptId combination from the respective relations.
- Query II requires that all tuples (u) in EMP have a matching EmpName in t, and there exists a matching DeptId in DEPT for each tuple (t). This means that the tuples (t) must have a valid EmpName for all tuples in EMP and a valid DeptId from DEPT.
- Query III requires that there exists a matching EmpName in EMP for each tuple (t), and all tuples (v) in DEPT have a matching DeptId in t. This means that the tuples (t) must have a valid EmpName from EMP and a valid DeptId for all tuples in DEPT.
The correct answer:
Based on the analysis, the correct answer is option 'D' (I, II, and III) as all three queries involve valid combinations of EmpName and DeptId from the EMP and DEPT relations.
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Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer?
Question Description
Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer?.
Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer?.
Solutions for Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? in English & in Hindi are available as part of our courses for GATE.
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Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer?, a detailed solution for Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? has been provided alongside types of Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice Consider a database that has the relation schemas EMP (EmpId, EmpName, DepId), and DEPT(DeptName, DeptId). Note that the DepId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.I.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∀ v ∈ DEPT (t[DeptId] ≠ DeptId]))}II.{t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] ≠ DeptId]))}III. {t | ∃ u ∈ EMP (t[EMPName] = u[EmpName] ∧ ∃ v ∈ DEPT (t[DeptId] = DeptId]))}a)I and II onlyb)I and III onlyc)II and III onlyd)I, II, and IIICorrect answer is option 'D'. Can you explain this answer? tests, examples and also practice GATE tests.
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