| left_key | No | Key column name(s) in the left file; leave out to auto-detect. Use a list for a composite key, e.g. "customer_id" or ["First Name","Last Name"]. | |
| join_type | No | left (default, like VLOOKUP): keep every left row and add matching right columns. inner: only rows found in both. full: everything from both files, matched where possible. Example: left. | |
| left_file | No | The main file whose rows you keep (CSV, TSV or .xlsx), e.g. orders.csv. A workbook with two sheets can be passed alone: sheet 1 is joined to sheet 2. | |
| right_key | No | Key column name(s) in the right file; leave out to auto-detect. Use a list for a composite key, e.g. "Customer ID" or ["First Name","Last Name"]. | |
| duplicates | No | When a key appears more than once in the right file: all (default) keeps every match and warns about the extra rows; first keeps only the first match, like VLOOKUP. Example: first. | |
| left_sheet | No | Sheet name in the left workbook, e.g. Orders. Default: the first sheet with data. | |
| left_table | No | Only when no file is attached: the left (main) table pasted as CSV or tab-separated text with a header row, e.g. "order_id,customer_id,amount\nSO-1,C123,40.00". | |
| right_file | No | The lookup file whose columns are added (CSV, TSV or .xlsx), e.g. customers.xlsx. | |
| right_sheet | No | Sheet name in the right workbook, e.g. Customers. Default: the first sheet with data (or the second sheet when both tables are in one workbook). | |
| right_table | No | Only when no file is attached: the right (lookup) table pasted as CSV or tab-separated text with a header row, e.g. "customer_id,name\nC00123,Acme Supply". | |
| left_header_row | No | Only if the headings were detected wrongly: the row number of the left file's header (counting non-blank rows in a CSV, sheet rows in Excel), e.g. 4. | |
| right_header_row | No | Only if the headings were detected wrongly: the row number of the right file's header, e.g. 3. | |
| skip_normalizations | No | Key clean-ups to turn OFF when IDs that differ only that way are really different, e.g. ["case"] for case-sensitive IDs or ["zeros"] when 0123 and 123 are different codes. Options: trim, case, unicode, excel, separators, zeros, prefix. | |