HubSpot expects one value per contact field, but when you have multiple child records for each parent contact, standard imports fail with “duplicate record” errors because the system can’t handle multiple rows with the same contact identifier.
The solution is to flatten your parent-child hierarchy by aggregating child records into single parent fields before importing, eliminating duplicate rows while preserving all your data.
Flatten parent-child data structures using Coefficient
Coefficient provides a data transformation layer that eliminates import errors by letting you aggregate child records before they reach HubSpot . Import your hierarchical data, transform it using spreadsheet formulas, then export clean, flattened records to HubSpot .
How to make it work
Step 1. Import your parent-child data structure.
Connect to your data source via Coefficient and import with full parent-child relationships visible. Include child record identifiers and values while keeping the parent contact ID as your key field for aggregation.
Step 2. Transform using aggregation formulas.
In Google Sheets, use =QUERY(A:C, “SELECT A, GROUP_CONCAT(B, ‘, ‘) GROUP BY A”, 1) to group child records by parent. Alternatively, create unique parents with =UNIQUE(FILTER(A:A, A:A<>“”)) and aggregate children with =TEXTJOIN(“, “, TRUE, FILTER($B:$B, $A:$A=E2)).
Step 3. Validate error-free data.
Ensure no duplicate parent IDs remain using =COUNTIF(E:E, E2)=1, check field length limits with =LEN(F2)<=65536, and verify proper text encoding for special characters. Preview your data before import to catch any formatting issues.
Step 4. Execute clean import.
Use Coefficient’s Export feature with Contact ID as the unique identifier. Map your aggregated child data to the target field, choose UPDATE action to modify existing contacts, and enable “Skip records with errors” for additional safety.
Import your hierarchical data without errors
This approach handles variable child record counts automatically while maintaining all data relationships in a flattened structure that HubSpot can process without errors. Start using Coefficient to eliminate your parent-child import issues.