[knz42]

SQL is not a single language but rather a family of languages. Each RDBMS that advertises support for SQL ends up implementing a different flavor of SQL, most of the times they are not even compatible :)

For now CockroachDB's supports a subset of the SQL implemented by other databases, with some extensions of its own. This subset will grow over time.

The two levels of isolation offered are snapshot (SI) and serializable (SSI). Snapshot means that concurrent transactions are atomic with regards to each other and "see" the same initial state from the DB. Serializable adds into this that they can't introduce write skews, ie if there are concurrent transactions they will "see" each others effects in some order.