Seaquel
SQL Server error code

SQL Server error 6809

SQL Server raises error 6809 at severity 16, which marks a problem with the query or data that you can correct.

Unnamed tables cannot be used as XML identifiers as well as unnamed columns cannot be used for attribute names. Name unnamed columns/tables using AS in the SELECT statement.
Msg6809
Severity16
Group6000–6999

Source: Database Engine events and errors