• It cannot filter query results based on date range
• Some common SQL functions are not currently supported
• It cannot join tables from different databases

The correct answer is: Some common SQL functions are not currently supported

Explanation: One key limitation of AMC SQL is that some common SQL functions are not currently supported. While AMC supports many standard SQL operations, some functions found in traditional SQL environments (such as GETDATE(), certain advanced window functions, or SELECT *) are either limited or unsupported due to privacy, security, and clean room requirements.

Reference content:

From the official Amazon Marketing Cloud SQL documentation: Amazon Marketing Cloud SQL limitations

“AMC does not support the GETDATE() function, which returns the current database system date and time. However, you may use the following as a workaround.”