Merge CSV/XLSX files and align mismatched headers

Merging files becomes tricky when different sources don’t share the same headers:

• One file has Email, another has email_address
• Columns appear in different orders
• Some columns exist only in certain files

The safest approach is to align by column name and fill missing cells with empty values.

Step-by-step strategy

1) Normalize column names

If you control the upstream export, keep a consistent naming convention:

• Use a single case: snake_case or Title Case
• Avoid trailing spaces
• Avoid duplicated headers

If you don’t control upstream files, do a quick pass to rename columns before merging.

2) Build a “master” header list

When merging multiple files, create the union of all headers:

• Start with the first file’s header
• Add any new columns found in the next files
• Keep ordering stable (don’t shuffle columns every time)

3) Re-map each row into the master header

For every row, create an output record where:

• Each master header has a value (or empty string)
• Missing columns become empty
• Extra columns are preserved

This prevents “column drifting” when you import the merged file into other tools.

Oriah Sheet behavior

Oriah Sheet merges CSV and XLSX inputs and:

• Aligns by column name
• Fills missing values with empty strings
• Lets you export as CSV (choose delimiter) and/or XLSX

Common pitfalls to avoid

• Duplicate header names: name appearing twice causes ambiguity.
• Whitespace issues: Email vs Email are different columns.
• Mixed encodings: one CSV might be UTF‑8, another Windows‑1252.

If you suspect encoding issues, re-export as UTF‑8 when possible.