What is the External ID in Salesforce and Data Wizard?

In Salesforce, an external ID is a unique identifier for records generated outside of Salesforce. This is a custom field that can be added to any object and used to reference records in Salesforce from external systems.

External IDs help you integrate data between Salesforce and other systems by providing a way to match records across different databases. External IDs let you automatically sync and update data between Salesforce and external systems without manual intervention.

External IDs can be set as text, auto-number, number, and email fields and marked as unique so that each record has a unique identifier. You can also create indexes to retrieve data faster and support efficient queries.

Salesforce allows you to create up to 25 external IDs per object. However, the number of external IDs you can create may vary depending on which edition of Salesforce you have and the number of custom fields available in your org.

Note that external IDs count against the total custom field limit. So if you hit your custom field limit, you may not be able to create additional external IDs. External IDs can affect data import, export, and query performance in Salesforce, so it's also important to carefully plan and consider your business needs before creating external IDs.

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Advantages

There are several advantages of using External IDs in Salesforce:

Integrate: External identities provide a more efficient way to integrate data between Salesforce and other systems. External IDs make it easy to match records across different systems, simplifying data synchronization and ensuring data consistency across systems.
Unique Identifier: The external ID provides a unique identifier for the record that can be used to reference it from other systems. This avoids duplication and confusion when working with data in different systems.
Query optimization: Using the external ID as a unique identifier allows you to optimize your queries to retrieve data faster. Indexing external IDs can speed up data retrieval and improve performance when working with large datasets.
Migrate data: You can migrate data from other systems to Salesforce using external identities. Mapping external IDs to Salesforce records makes importing data easier and ensures that it's correctly linked to existing records.
Business logic: External IDs can be used to support complex business logic that requires referencing data across different systems. External identities allow you to create custom workflows and automation based on data from external systems, helping streamline business processes and improve efficiency. Overall, external identities provide a powerful way to integrate data across disparate systems, support complex business logic, streamline queries, and improve performance.

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Cons

While external IDs in Salesforce have some advantages, there are also some potential disadvantages to consider.

Availability Limit: Salesforce has a limit of 25 external IDs per object. This means that if you have multiple points of integration or complex data requirements, you may run out of available external identities.
Maintenance: Adding or removing external IDs can impact your data model as it requires changing the relationships between records. This can make maintaining and changing your Salesforce org more difficult.
Performance: External IDs can improve query performance, but they can also slow down data imports and exports if not used properly. This is because Salesforce must validate external IDs when importing data, which can add overhead and processing time.
Complexity: Managing external identities can add complexity to your data model, especially if you need to track multiple external identities across different objects. This can make the data difficult to understand and manipulate over time.
Security: External IDs can be used to reference data from external systems. This can pose security concerns when sensitive data is involved. Before implementing external identities in your organization, it's important to carefully consider the security implications of using external identities. Overall, external IDs provide a convenient way to integrate data between Salesforce and other systems, but they come with certain complexities and potential performance implications that you should carefully consider before implementing them in your organization, also poses problems.