For each part of this problem you will need to construct a single SQL query which will check whether a certain condition holds on a specific instance of a relation, in the following way: your query should return an empty result if and only if the condition holds on the instance. (If the condition doesn't hold, your query should return something non-empty). Note our language here: the conditions that we specify cannot be proved to hold in general without knowing the externally-defined functional dependencies; so what we mean is, check whether they could hold in general for the relation, given a specific set of tuples. You may assume that there will be no NULL values in the tables, and you may assume that the relations are sets rather than multisets, but otherwise your query should work for general in- stances. 1. A is a superkey for a relation T (A, B, C, D). 2. The combinations of two attributes in the relation T (A, B, C, D) are each keys. 3. A tuple-generating dependency (TGD) between two relations A and B, having some shared attributes X₁,..., Xn, holds if, for every tuple ta in A, there is some tuple tg in B such that tA[X₂] = tB[X₂] for i = 1, ...n. In other words, for every distinct tuple in A, there must exist a corresponding tuple in B, which has the same values of shared attributes. Consider three tables Sailors(sid, sname, rating, age), Reserves(sid, bid, sname, bname, date) and Boats (bid, bname, color); Check for a TGD between Sailors and Reserves.
For each part of this problem you will need to construct a single SQL query which will check whether a certain condition holds on a specific instance of a relation, in the following way: your query should return an empty result if and only if the condition holds on the instance. (If the condition doesn't hold, your query should return something non-empty). Note our language here: the conditions that we specify cannot be proved to hold in general without knowing the externally-defined functional dependencies; so what we mean is, check whether they could hold in general for the relation, given a specific set of tuples. You may assume that there will be no NULL values in the tables, and you may assume that the relations are sets rather than multisets, but otherwise your query should work for general in- stances. 1. A is a superkey for a relation T (A, B, C, D). 2. The combinations of two attributes in the relation T (A, B, C, D) are each keys. 3. A tuple-generating dependency (TGD) between two relations A and B, having some shared attributes X₁,..., Xn, holds if, for every tuple ta in A, there is some tuple tg in B such that tA[X₂] = tB[X₂] for i = 1, ...n. In other words, for every distinct tuple in A, there must exist a corresponding tuple in B, which has the same values of shared attributes. Consider three tables Sailors(sid, sname, rating, age), Reserves(sid, bid, sname, bname, date) and Boats (bid, bname, color); Check for a TGD between Sailors and Reserves.
Computer Networking: A Top-Down Approach (7th Edition)
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![For each part of this problem, you will need to construct a single SQL query which will check whether a certain condition holds on a specific instance of a relation, in the following way: your query should return an empty result if and only if the condition holds on the instance. (If the condition doesn’t hold, your query should return something non-empty).
Note our language here: the conditions that we specify cannot be proved to hold in general without knowing the externally-defined functional dependencies; so what we mean is, check whether they could hold in general for the relation, given a specific set of tuples.
You may assume that there will be no NULL values in the tables, and you may assume that the relations are sets rather than multisets, but otherwise your query should work for general instances.
1. A is a superkey for a relation T (A, B, C, D).
2. The combinations of two attributes in the relation T (A, B, C, D) are each keys.
3. A tuple-generating dependency (TGD) between two relations A and B, having some shared attributes \(X_1, ..., X_n\), holds if, for every tuple \( t_A \) in A, there is some tuple \( t_B \) in B such that \( t_A[X_i] = t_B[X_i] \) for i = 1, ...n.
In other words, for every distinct tuple in A, there must exist a corresponding tuple in B, which has the same values of shared attributes.
Consider three tables Sailors(\(sid, sname, rating, age\)), Reserves(\(sid, bid, sname, bname, date\)) and Boats(\(bid, bname, color\)); Check for a TGD between Sailors and Reserves.
4. A multivalued dependency (MVD) is defined as follows: let R be a schema i.e. a set of attributes, and consider two sets of attributes \(X \subseteq R\) and \(Y \subseteq R \).
We say that a multivalued dependency (MVD), written: \(X \twoheadrightarrow Y\), holds on R if whenever there are two tuples \( t_1 \), \( t_2 \) such that \( t_1[X] = t_2[X] \), there also exists a third tuple \( t_](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fb36a6f85-01d5-49e3-a43c-f9c64c0085d9%2F0ab97b5d-c628-440e-9b1b-255d2669c04b%2Fjclr9jj_processed.png&w=3840&q=75)
Transcribed Image Text:For each part of this problem, you will need to construct a single SQL query which will check whether a certain condition holds on a specific instance of a relation, in the following way: your query should return an empty result if and only if the condition holds on the instance. (If the condition doesn’t hold, your query should return something non-empty).
Note our language here: the conditions that we specify cannot be proved to hold in general without knowing the externally-defined functional dependencies; so what we mean is, check whether they could hold in general for the relation, given a specific set of tuples.
You may assume that there will be no NULL values in the tables, and you may assume that the relations are sets rather than multisets, but otherwise your query should work for general instances.
1. A is a superkey for a relation T (A, B, C, D).
2. The combinations of two attributes in the relation T (A, B, C, D) are each keys.
3. A tuple-generating dependency (TGD) between two relations A and B, having some shared attributes \(X_1, ..., X_n\), holds if, for every tuple \( t_A \) in A, there is some tuple \( t_B \) in B such that \( t_A[X_i] = t_B[X_i] \) for i = 1, ...n.
In other words, for every distinct tuple in A, there must exist a corresponding tuple in B, which has the same values of shared attributes.
Consider three tables Sailors(\(sid, sname, rating, age\)), Reserves(\(sid, bid, sname, bname, date\)) and Boats(\(bid, bname, color\)); Check for a TGD between Sailors and Reserves.
4. A multivalued dependency (MVD) is defined as follows: let R be a schema i.e. a set of attributes, and consider two sets of attributes \(X \subseteq R\) and \(Y \subseteq R \).
We say that a multivalued dependency (MVD), written: \(X \twoheadrightarrow Y\), holds on R if whenever there are two tuples \( t_1 \), \( t_2 \) such that \( t_1[X] = t_2[X] \), there also exists a third tuple \( t_
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