Understanding the MERGE Operation in SQL Server: Workarounds for Failed Constraints

Merging Multiple Date Columns in a Pandas DataFrame: A Comparative Analysis of melt() and unstack() Methods

Performing Case-Insensitive Joins on Keys with Non-Alphanumeric Characters in Python Pandas

Merging Two Similar DataFrames Using Conditions with Pandas Merging

Here is a complete code snippet that combines all the interleaved code you wrote in a nice executable codeblock:

Merging Tables by Looking Up Multiple Column Values Using Pandas