Does the following equation hold, i.e. are the operators “selection” and “projection” commutative in this case? R is an arbitrary relation with possibly more columns than c1, c2, c3.

π(c1, c2, c3) (σ(c2=literal) (R)) = σ(c2=literal) (π(c1, c2, c3)(R))

Select one:

• Yes, always.
• Conditionally, if we can ascertain that there are no duplicates in the (c1, c2, c3) of R.
• No, never.
• Conditionally, if the column c2 has only distinct values.