Consider the relations $r(A, B)$ and $s(B, C)$, where $s.B$ is a primary key and $r.B$ is a foreign key referencing $s.B$. Consider the query
$Q: r \bowtie (\sigma_{B<5} (s))$
Let LOJ denote the natural left outer-join operation. Assume that $r$ and $s$ contain no null values.
Which of the following is NOT equivalent to $Q$?
- $\sigma_{B<5} (r \bowtie s)$
- $\sigma_{B<5} (r \: LOJ \: s)$
- $r \: LOJ \: (\sigma_{B<5} (s))$
- $\sigma_{B<5} (r) \: LOJ \: s$