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Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
References an external table by name.
Note
The external_table function has similar restrictions as the table function.
Standard query limits apply to external table queries as well.
To accelerate queries over external delta tables, see Query acceleration policy.
Syntax
external_table( TableName [, MappingName / MaxAgeOverride ] )
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| TableName | string |
✔️ | The name of the external table being queried. Must reference an external table of kind blob, adl, or sql. |
| MappingName | string |
A name of a mapping object that maps fields in the external data shards to columns output. | |
| MaxAgeOverride | TimeSpan |
When Query Acceleration Policy is enabled, override the policy's MaxAge property for this query. If you use this property, the external table returns accelerated data if the last index refresh time is greater than @now - MaxAgeOverride. Minimum: 1s |
Authentication and authorization
The authentication method to access an external table is based on the connection string provided during its creation, and the permissions required to access the table vary depending on the authentication method. For more information, see Azure Storage external table or SQL Server external table.
Use in update policy queries
The external_table() function can be used inside update policy queries under restricted conditions:
- The external table must have a query acceleration policy enabled.
- The query acceleration
Hotperiod must cover all data in the external table (currently >= 100 years).
- If the external table uses impersonation authentication, the update policy must be configured with a
ManagedIdentity.
- In Fabric, the system automatically handles authorization through the
OwnerPrincipalDetailsproperty on the update policy, which captures the identity of the user who sets or alters the policy.
For more information, see Update policy overview - Query limitations.