How can I enable serverless SQL warehouses in my Databricks workspace and what are the requirements and limitations?
To enable serverless SQL warehouses in your Databricks workspace, follow these steps:

1. Ensure your Databricks account meets the requirements:
   - It's not on a free trial.
   - It's on the Premium plan or above.
   - Your workspace control plane and serverless compute plane are in a region that supports Databricks SQL Serverless.
   - Your workspace does not use S3 access policies.
   - Your workspace does not use an external Hive legacy metastore.

2. Enable serverless compute in your account by going to the feature enablement tab of the account console settings page and accepting the additional terms.

3. Optionally, update the instance profile for serverless compute if your workspace uses an instance profile created before June 24, 2022, for data access.

As for limitations, serverless warehouses have the following:

1. Cluster policies, including spot instance policies, are unsupported.
2. Customer-managed VPCs are not applicable to compute resources for serverless SQL warehouses.
3. Serverless SQL warehouses use private connectivity between the Databricks control plane and the serverless compute plane in nearly all cases.
4. Serverless SQL warehouses do not have public IP addresses.
5. Serverless SQL warehouses do not use customer-managed keys for EBS storage encryption.

Keep in mind that serverless SQL warehouses support the compliance security profile in some regions, and they have hardened images, encrypted inter-node communication, anti-virus monitors, file integrity monitors, and auto-restart for long-running serverless SQL warehouses in those regions. Outside those regions, if the compliance security profile is enabled on a workspace, Databricks does not allow starting serverless SQL warehouses.