No column name was specified for column [n] of 'a'

Error Message

When validating SQL with a computed column in a Query Layer in SQL Server, the following error may occur.

Underlying DBMS error: ~ No column name was specified for column [n] of 'a'.

Cause

A column alias is not specified for a computed column.

When a query layer is initially created, the user defined query is utilized as a sub-query to select the geometry column.

For example:

Code:
SELECT objectid, shape.STConvexHull() as shape2 FROM sde.mySpatialTable

Code:
exec sp_prepare @p1 ...,N'select shape2 from (SELECT objectid, shape.STConvexHull() as shape2 
FROM sde.mySpatialTable) a',1

Code:
SELECT objectid, shape.STConvexHull() FROM sde.mySpatialTable

Underlying DBMS error [[Microsoft][SQL Server Native Client 10.0][SQL Server} 
No column name was specified for column 2 of 'a'.] 

Solution or Workaround

Code:
SELECT shape.STConvexHull() AS MyConvexHull FROM MySpatialTable;