Focused purpose
What this tool does
Join two CSV or TSV files locally with inner, left, right or full joins. Preview duplicate keys, unmatched rows and column collisions without an account.
- ✓ Inner, left, right and full joins
- ✓ Independent key columns
- ✓ Duplicate-key estimate
- ✓ Collision-safe column names
Workflow
How to use it
- 01
Open exactly two tables.
- 02
Choose keys and inspect uniqueness.
- 03
Select join type, preview cardinality and export.
Available controls
Available options
- Choose a key in each file.
- Select join type.
- Prefix or rename colliding columns.
- Export unmatched rows separately.
Orders joined to customers
Example before and after
A left join must enrich orders while keeping an unmatched order.
Before
orders.csv order_id,customer_id A1,2 A2,3 customers.csv customer_id,name 2,Linus 4,Grace
After
order_id,customer_id,name A1,2,Linus A2,3,
Expected result: The matching name is added and the unmatched order stays visible.
Practical scenarios
Common use cases
Add customer names to orders.
Match inventory with prices.
Find records missing from a reference table.
HONEST LIMITS
Important limitations
- iDuplicate keys create one row per matching pair.
- iFuzzy or approximate matching is not performed.
FAQ
Questions about this tool
Which join keeps every left row?
A left join keeps all rows from the first table and adds matches from the second.
What happens with duplicate keys?
Every matching pair is produced; the cardinality estimate warns about row multiplication.
How are identical column names handled?
Key columns are reconciled and other collisions receive explicit prefixes or selected names.