# Data Import Wizard, Data Loader and external IDs

*Platform Administrator II Study Guide · Data and Analytics Management · Last updated October 26, 2026 · https://www.certifyforce.com/study-guide/platform-administrator-ii/data-and-analytics-management/data-import-wizard-data-loader-and-external-ids*

Pick the Data Import Wizard or Data Loader from the object, volume and operation; automate loads with the Data Loader command line; relate records with external IDs during upsert (and know where polymorphic fields stop you); and tune Bulk API settings for nulls, locking and assignment rules.

- Certification: Salesforce Platform Administrator II
- Exam section: Data and Analytics Management
- Study guide: https://www.certifyforce.com/study-guide/platform-administrator-ii

**Official exam objective:**

> Given a scenario, identify the appropriate tools and methods for importing data into Salesforce (data import wizard, data loader, and external ID).

## What the exam expects

- Choose the Data Import Wizard, Data Loader or another tool from the object, record count, operation and install constraints.
- Plan an unattended, scheduled load with the Data Loader command-line interface and pick the right host.
- Relate child records to parents by external ID during a Data Loader upsert, and recognise polymorphic fields that can't use one.
- Set Data Loader options for Bulk API: batch size, clearing fields with nulls, serial mode for locking errors, and assignment rules.
- Predict which save-time rules still apply to imported records.

Key terms: **upsert** (insert or update in one pass, matching on an ID or external ID); **external ID** (a custom field flagged to hold another system's unique identifier for matching); **polymorphic field** (a lookup that can point at several object types, such as an activity's Related To); **Bulk API** (asynchronous, parallel loading API); **serial mode** (Bulk API batches processed one at a time).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Data Import Wizard volume | Up to 50,000 records | [Choosing a Method](https://help.salesforce.com/s/articleView?id=sf.import_which_data_import_tool.htm&language=en_US&type=5) |
| Data Loader volume | Between 5,000 and 5 million | [Choosing a Method](https://help.salesforce.com/s/articleView?id=sf.import_which_data_import_tool.htm&language=en_US&type=5) |
| Wizard operations | Import only; no export or delete | [Choosing a Method](https://help.salesforce.com/s/articleView?id=sf.import_which_data_import_tool.htm&language=en_US&type=5) |
| Wizard unmapped column | Not imported; Account Note or Contact Note keeps the text | [Data Import Wizard](https://help.salesforce.com/s/articleView?id=sf.import_with_data_import_wizard.htm&language=en_US&type=5) |
| Data Loader command line | Windows only | [Data Loader](https://help.salesforce.com/s/articleView?language=en_US&id=xcloud.data_loader_about.htm&type=5) |
| External ID mapping | Upsert, related-objects step, [Object]:[ExternalIDField__c] | [External ID upsert](https://help.salesforce.com/s/articleView?id=000383207&language=en_US&type=1) |
| Polymorphic fields | WhatId, WhoId, custom object Owner can't map to external IDs | [External ID upsert](https://help.salesforce.com/s/articleView?id=000383207&language=en_US&type=1) |
| Bulk API batch size | Up to 10,000 (SOAP 200) | [Configure Data Loader](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/configuring_the_data_loader.htm) |
| Null with Bulk API | Use #N/A; Insert null values unavailable | [Configure Data Loader](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/configuring_the_data_loader.htm) |
| Locking errors | Enable serial mode for Bulk API | [Configure Data Loader](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/configuring_the_data_loader.htm) |
| Assignment rule setting | Rule ID; cases and leads; overrides Owner | [Configure Data Loader](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/configuring_the_data_loader.htm) |

## Check yourself

- When does an import that fits under 50,000 records still need Data Loader?
- When would you map a wizard column to Contact Note?
- Why does a Data Loader row that matches an alert-only duplicate rule fail instead of showing an alert?
- What does serial mode trade away to fix locking errors?

## Sources

- [Choosing a Method for Importing Data](https://help.salesforce.com/s/articleView?id=sf.import_which_data_import_tool.htm&language=en_US&type=5)
- [Import Data with the Data Import Wizard](https://help.salesforce.com/s/articleView?id=sf.import_with_data_import_wizard.htm&language=en_US&type=5)
- [Data Loader](https://help.salesforce.com/s/articleView?language=en_US&id=xcloud.data_loader_about.htm&type=5)
- [Data Loader Command Line Introduction](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/command_line_intro.htm)
- [Import Related Records with an External ID in Salesforce Data Loader](https://help.salesforce.com/s/articleView?id=000383207&language=en_US&type=1)
- [Configure Data Loader](https://developer.salesforce.com/docs/atlas.en-us.dataLoader.meta/dataLoader/configuring_the_data_loader.htm)
- [Custom Field Types](https://help.salesforce.com/s/articleView?id=platform.custom_field_types.htm&type=5)
- [Things to Know About Duplicate Rules](https://help.salesforce.com/s/articleView?language=en_US&id=sales.duplicate_rules_overview.htm&type=5)
- [Validation Rules](https://help.salesforce.com/s/articleView?id=platform.fields_about_field_validation.htm)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 8 linked practice questions, and unlimited timed mock exams are included with the Platform Administrator II pack (USD $19): https://www.certifyforce.com/practice-exams