Does SQL92's REPEATABLE-READ preclude Write Skew (A5B)?
Does REPEATABLE READ preclude Write Skew?


Yes - if you buy into the Critique's view that the ANSI definitions were based on locking behaviours, for example:


  Remark 6. The locking isolation levels of Table 2 and the phenomenological definitions of Table 3 are equivalent. Put another way, PO, PI, P2, and P3 are disguised redefinitions of Locking behavior.


From that viewpoint, the history:

r1[x]...r2[y]...w1[y]...w2[x]...(c1 and c2 occur)


...is prevented when long-duration read shared locks are taken, because w1[y] is blocked by the lock taken by r2[y]. Similarly, w2[x] would be blocked by the lock taken by r1[x]. Therefore, this history cannot arise.

No - if you literally interpret the ANSI definitions. These are widely seen to be incomplete, so this outcome is not really all that surprising.