### Answer: True

**Explanation:**
In relational algebra, selection (σ) is considered a commutative operation. This means that if you have two selection operations, the order in which you apply them does not affect the result. For example, if you have two predicates P1 and P2, then:

$$
\sigma_{P1}(\sigma_{P2}(R)) = \sigma_{P2}(\sigma_{P1}(R))
$$

On the other hand, projection (π) is not commutative. The order of projection matters because projecting different attributes in various orders can yield different results. For example, projecting attributes A and B from a relation R is not the same as projecting B and A. Thus:

$$
\pi_{A, B}(R) \neq \pi_{B, A}(R)
$$

Since the statement says that selection is commutative while projection is not, this statement is **True**.

Question

### Answer: True

**Explanation:**  
In relational algebra, selection (σ) is considered a commutative operation. This means that if you have two selection operations, the order in which you apply them does not affect the result. For example, if you have two predicates P1 and P2, then:

$$
\sigma_{P1}(\sigma_{P2}(R)) = \sigma_{P2}(\sigma_{P1}(R))
$$

On the other hand, projection (π) is not commutative. The order of projection matters because projecting different attributes in various orders can yield different results. For example, projecting attributes A and B from a relation R is not the same as projecting B and A. Thus:

$$
\pi_{A, B}(R) \neq \pi_{B, A}(R)
$$

Since the statement says that selection is commutative while projection is not, this statement is **True**.

Knowee AI · Accepted Answer

### Answer: True

**Explanation:**  
In relational algebra, selection (σ) is considered a commutative operation. This means that if you have two selection operations, the order in which you apply them does not affect the result. For example, if you have two predicates P1 and P2, then:

$$
\sigma_{P1}(\sigma_{P2}(R)) = \sigma_{P2}(\sigma_{P1}(R))
$$

On the other hand, projection (π) is not commutative. The order of projection matters because projecting different attributes in various orders can yield different results. For example, projecting attributes A and B from a relation R is not the same as projecting B and A. Thus:

$$
\pi_{A, B}(R) \neq \pi_{B, A}(R)
$$

Since the statement says that selection is commutative while projection is not, this statement is **True**.

Selection is commutative, but projection is not commutative:Question 4Select one:TrueFalse

Question

Selection is commutative, but projection is not commutative:

Solution

Answer: True

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