One table split across sheets

• A new sheet was started each period to keep things manageable.
• Each team or site kept its own copy of the same template.
• A system limited the size of each export, so the data arrived in pieces.

• No question that spans sheets can be answered without combining them by hand each time.
• The fact that distinguishes the sheets lives in a tab or file name, where formulas and imports do not see it.
• The sheets drift apart: a column is added to one, renamed in another, and reordered in a third.

• Look for tabs or files named after periods, places, or people, each with a similar layout.
• Compare the headers of every sheet. Small differences show where the copies have drifted.
• Check for rows that appear in more than one sheet, such as a record carried over from one month to the next.

• Add a column to each sheet for whatever its name was recording, before combining.
• Bring the column names and order into agreement. See inconsistent column names across files.
• Stack the sheets into one table, and check that the combined row count equals the sum of the parts.
• Check for overlap afterward. Whether a row repeated across sheets is a duplicate or a real repeat is a judgment about the data.

• Inconsistent column names across filesFiles that should share one layout name the same column differently, or use the same name for different things.
• Wide tables that should be longValues of one variable, such as months or years, are spread across the column headers instead of being stored in a column of their own.
• Exact duplicate rowsThe same row appears more than once, identical in every column.

TermsSpreadsheet, Schema, Provenance, Tidy data