São expressões corretas no MS SQL Server, os exemplos:...

DROP COLUMN table_name column_name e SELECT FROM table_name AVG(column_name)

DROP INDEX index_name ON table_name e SELECT FROM table_name AVG(column_name)

DROP COLUMN table_name column_name e SELECT AS alias_name column_name(s) FROM table_name

DROP INDEX index_name ON table_name e ALTER COLUMN TABLE table_name column_name datatype

DROP INDEX table_name.index_name e SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,...)