Use a Column Alias in Nested select Statements

You can use an column alias in the select list of nested select statements.

The column alias uses one of these forms:
For example, this example is equivalent to a select statement with the as tableid clause removed:
1> select *
2> from syscolumns c
3> where in (
4> select as tableid
5> from sysobjects o
6> where like '%attr%')
SAP ASE ignores the alias (the allowed column heading) in this example.