{"id":697,"date":"2026-09-23T23:01:46","date_gmt":"2026-09-23T14:01:46","guid":{"rendered":"https:\/\/jim-jin.com\/?p=697"},"modified":"2026-10-08T09:10:02","modified_gmt":"2026-10-08T00:10:02","slug":"%e8%a4%87%e6%95%b0%e3%81%aecsv%e3%82%921%e3%81%a4%e3%81%ab%e3%81%be%e3%81%a8%e3%82%81%e3%82%8b%e6%96%b9%e6%b3%95%ef%bd%9c%e8%a6%8b%e5%87%ba%e3%81%97%e3%81%ae%e9%87%8d%e8%a4%87%e3%83%bb%e5%88%97","status":"publish","type":"post","link":"https:\/\/jim-jin.com\/en\/posts\/697","title":{"rendered":"Combine Multiple CSV Files | Avoid Duplicate Headers and Column Mismatches"},"content":{"rendered":"\n

CSV merging helps combine a year’s monthly sales, product lists from multiple stores, or exports from different systems into one file.<\/p>\n\n\n\n

Simply pasting files below one another can leave repeated headers inside the data or swap product-name and product-code columns.<\/p>\n\n\n\n

Before combining CSVs, check header handling, field names and column order, and encoding.<\/strong><\/p>\n\n\n\n

This article explains preparation, merging with JIM-JIN’s Excel \/ CSV Merge and Split Tool, and checks afterward.<\/p>\n\n\n\n

Excel \/ CSV Merge and Split Tool (Free)<\/span><\/a><\/div>\n\n\n\n

Use “Append rows” to combine CSV lists<\/h2>\n\n\n\n

There are two main ways to combine CSVs.<\/p>\n\n\n\n

Merge method<\/th>How data is combined<\/th>Example task<\/th><\/tr><\/thead>
Append rows<\/td>Add data rows to create one table<\/td>Combine monthly sales into a year’s list<\/td><\/tr>
Join by a shared column<\/td>Match product codes or other keys and add fields<\/td>Add stock quantities from another file to a product list<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

To combine multiple CSVs into one list, normally use “Append rows.”<\/p>\n\n\n\n

For example, April’s 100 sales records plus May’s 120 records should produce 220 data records, excluding headers.<\/p>\n\n\n\n

Adding prices from another file to rows with the same product code is a horizontal join. Choose the method that matches your goal.<\/p>\n\n\n\n

Excel \/ CSV Merge and Split Tool (Free)<\/span><\/a><\/div>\n\n\n\n

Three common CSV merging problems<\/h2>\n\n\n\n
\"Avoid<\/figure>\n\n\n\n

Problem 1: Header rows appear inside the data<\/h3>\n\n\n\n

If every CSV includes headers such as “Product code”, “Product name”, and “Quantity”, simple concatenation leaves headers at file boundaries.<\/p>\n\n\n\n

Product code<\/th>Product name<\/th>Quantity<\/th><\/tr><\/thead>
00123<\/td>Ballpoint pen<\/td>10<\/td><\/tr>
00045<\/td>Notebook<\/td>5<\/td><\/tr>
Product code<\/td>Product name<\/td>Quantity<\/td><\/tr>
00789<\/td>Sticky notes<\/td>8<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Those repeated field names are then treated as ordinary data.<\/p>\n\n\n\n

To prevent import errors and incorrect totals, treat each CSV’s first row as field names and organize the output header.<\/strong> This is necessary.<\/p>\n\n\n\n

\"Prevent<\/figure>\n\n\n\n

Problem 2: Different column orders place values in the wrong fields<\/h3>\n\n\n\n

CSVs containing the same fields do not necessarily use the same column order.<\/p>\n\n\n\n

Consider the following two CSVs.<\/p>\n\n\n\n

CSV A<\/strong><\/p>\n\n\n\n

Product code<\/th>Product name<\/th>Quantity<\/th><\/tr><\/thead>
00123<\/td>Ballpoint pen<\/td>10<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

CSV B<\/strong><\/p>\n\n\n\n

Product name<\/th>Quantity<\/th>Product code<\/th><\/tr><\/thead>
Notebook<\/td>5<\/td>00045<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Appending CSV B by position alone can put “Notebook” into the product-code column, breaking field-to-value correspondence.<\/p>\n\n\n\n

To combine them correctly, match field names and arrange values as follows.<\/p>\n\n\n\n

Product code<\/th>Product name<\/th>Quantity<\/th><\/tr><\/thead>
00123<\/td>Ballpoint pen<\/td>10<\/td><\/tr>
00045<\/td>Notebook<\/td>5<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Equal column counts do not guarantee equal column order.<\/strong> Check every file’s headers before merging.<\/p>\n\n\n\n

Problem 3: Different encodings cause partial garbling<\/h3>\n\n\n\n

Concatenating UTF-8 and Shift_JIS files without decoding them correctly can produce a file that no single encoding reads properly.<\/p>\n\n\n\n

Read each source using its correct encoding, then save the combined output in the destination’s required encoding.<\/p>\n\n\n\n

Matching file names or extensions do not guarantee matching encoding or delimiters.<\/p>\n\n\n\n

Excel \/ CSV Merge and Split Tool (Free)<\/span><\/a><\/div>\n\n\n\n

What to check before merging<\/h2>\n\n\n\n

Keep all original CSVs and verify the intended files before starting.<\/p>\n\n\n\n

Item<\/th>What to check<\/th><\/tr><\/thead>
Selected files<\/td>Have you selected the same file or an old version twice?<\/td><\/tr>
Reporting period<\/td>Are months or dates duplicated or missing?<\/td><\/tr>
Headers<\/td>Does the first row contain field names or data?<\/td><\/tr>
Field names<\/td>Do equivalent fields have different names?<\/td><\/tr>
Column order<\/td>Does the order differ between files?<\/td><\/tr>
Encoding<\/td>Can Japanese text be read correctly?<\/td><\/tr>
Delimiter<\/td>Are comma, tab, or other delimiter settings correct?<\/td><\/tr>
Record count<\/td>How many records should the combined file contain?<\/td><\/tr>
Output format<\/td>What encoding and column order does the recipient require?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

For sales amounts, check whether fields with the same name use different currencies or include\/exclude tax.<\/p>\n\n\n\n

Identical field names do not guarantee identical data meaning.<\/strong><\/p>\n\n\n\n

Excel \/ CSV Merge and Split Tool (Free)<\/span><\/a><\/div>\n\n\n\n

Combine files with JIM-JIN’s Excel \/ CSV Merge and Split Tool<\/h2>\n\n\n\n
\"Merge<\/figure>\n\n\n\n

JIM-JIN’s tool combines and splits multiple CSV or Excel files.<\/p>\n\n\n\n

When “Append rows” treats the first row as field names, it can align columns by name even when their order differs.<\/p>\n\n\n\n

Fields missing from a source file become empty. This helps you check differences that simple copying and pasting may overlook.<\/p>\n\n\n\n

Step 1: Choose merging and a processing method<\/h3>\n\n\n\n

Open the tool and select “Merge.”<\/p>\n\n\n\n

You can process on your computer or on the server. The default is processing on your computer.<\/p>\n\n\n\n

Server processing uploads files. Check the privacy notice, usage conditions, available methods, and limits shown on screen.<\/p>\n\n\n\n

Step 2: Add the CSVs to combine<\/h3>\n\n\n\n

Select the CSV files or drag and drop them.<\/p>\n\n\n\n

Review names and file count. Selecting the same CSV twice can duplicate its records.<\/p>\n\n\n\n

Check file order, such as chronological month order or your preferred store order.<\/p>\n\n\n\n

However, arranging files differs from sorting all data by date or another field.<\/strong> Also check the order within each file.<\/p>\n\n\n\n

Step 3: Review encoding, delimiters, and first-row handling<\/h3>\n\n\n\n

Check that Japanese text is readable and values are separated into the correct columns.<\/p>\n\n\n\n

Review encoding if text is garbled, or delimiters if all values appear in one column.<\/p>\n\n\n\n

If the first row contains field names, enable first-row header handling.<\/p>\n\n\n\n

Treating a headerless file as having headers can lose its first record. Treating a file with headers as headerless mixes field names into the data.<\/p>\n\n\n\n

If header and headerless settings are mixed, JIM-JIN asks you to make them consistent. Match the actual contents of every file.<\/p>\n\n\n\n

Step 4: Choose “Append rows”<\/h3>\n\n\n\n

Use “Append rows” for monthly, store-based, or similar lists.<\/p>\n\n\n\n

With first-row headers enabled, alignment uses field names rather than positions.<\/p>\n\n\n\n

Matching field names can align correctly even with different orders, for example:<\/p>\n\n\n\n