Differentiate between 'w' and 'a' file modes in Python.
\[ \begin{array}{|c|c|} \hline \textbf{File Mode} & \textbf{Description} \\ \hline 'w' & Opens the file for writing. Existing content is erased. \\ 'a' & Opens the file for appending. Data is added to the end. \\ \hline \end{array} \]
The SELECT statement when combined with \(\_\_\_\_\_\_\) clause, returns records without repetition.
In SQL, the aggregate function which will display the cardinality of the table is \(\_\_\_\_\_\).
myStr = "MISSISSIPPI"
print(myStr[:4] + "#" + myStr[-5:])