Added a sql (cte and union) to the concatenation of movie dataframes example

[DerikVo]

The above python code is equivalent to SQL's:

WITH all_movies_df AS (
    SELECT *
    FROM movies_df
    UNION ALL
    SELECT *
    FROM other_movies_df
)
SELECT *
FROM all_movies_df;

[DerikVo]

I noticed, some assignments on google class room still use the notebooks that utilize file pathways. I added a command to allow captains to let cooper's quickly download the dataset on their working colab environment. The link should be a folder titled "Content" with a capital C, and should only contain CSV if this code is to be adapted for other notebooks.

!gdown --folder https://drive.google.com/drive/folders/1DyiVBtUKIMg311TQTUoGt0kV2vcFcseM
!cd Content; mv *.csv ..; rmdir /content/Content