[DMDB] Note on sql

semester4/dmdb/parts/00_relational-model_logic/01_algebra/00_operators.tex

@@ -32,8 +32,8 @@
           In other words, $R \div S = T$, with $T$ being the \textit{largest} relation such that $S \times T \subseteq R$.
           (Find all rows that do not fulfil a condition)
 \end{itemize}
-% TODO: Add other join operations
-% TODO: Inequality joins (especially for SQL)
+Note that natural joins join on \textit{all} matching columns, i.e. the applied selection uses all matching columns in the predicate,
+which is also how it works in SQL!
 
 If we apply set semantics generally, then each operator returns results that adhere to that concept, even Projections!
 

semester4/dmdb/parts/01_sql/03_query-language/01_basic-operators.tex

@@ -36,4 +36,9 @@ or in \texttt{WHERE} clauses like this:
 This is referred to as a \bi{Self-Join} and can come in handy when comparing values in a single table,
 or to build pairs.
 
-We can use comparison operators also with subqueries containing aggregations, if they return a single result, for multiple results, need \texttt{ANY}, \texttt{ALL}, etc (see above)
+We can use comparison operators also with subqueries containing aggregations, if they return a single result, for multiple results, need \texttt{ANY}, \texttt{ALL}, etc (see above).
+
+They are applied as follows:
+\mint{sql}|SELECT * FROM Products WHERE price = ALL (SELECT Price FROM Products WHERE release_year = 2000)|
+
+To limit the number of returned tuples, use \texttt{LIMIT N}, where $N$ is to be replaced with any natural number