[DMDB] Fix issues, improve query processing with notes on time complexities

semester4/dmdb/parts/04_query-processing/04_join/00_simple-join.tex

@@ -13,4 +13,6 @@
         \EndProcedure
     \end{algorithmic}
 \end{algorithm}
-Here, the max output size is $T_R \cdot T_S$, where $T_X$ is the number of tuples for realtion $X$.
+Here, the max output size is $T_R \cdot T_S$, where $T_X$ is the number of tuples for relation $X$.
+
+The cost is obviously \cost{$\texttt{cnt}(R) \cdot \texttt{cnt}(S)$}, with $\texttt{cnt}(X)$ the number of tuples in $X$.