Combining Data From Multiple Sources

When I combine data from different sources with inconsistent formats, the first thing I do is standardize everything: dates, column names, booleans, numbers, etc., so they all speak the same language. After doing that, I'll:

• Align schemas: match columns across datasets. If one has extras, I drop or keep them depending on relevance.
• Unify categories: I clean up inconsistencies like "Y" vs. "Yes" to avoid downstream issues.
• Tag the source: I add a source column so I know where each row came from. This is super useful for tracking or debugging later.
• Merge or stack: If the structure is the same, I concat(). If I'm matching on something like customer ID, I go with a merge or join.
• Final clean-up: I look for duplicates, mismatched types, or broken values post-merge and fix them.

I avoid merging before checking data types or keys. That’s a fast track to lost or duplicated rows.