How turn text to SQL --> Select * ' From Emp'

This is just the foundation of my problem..... for example ..

Select * ' From Emp'

Or for example

Select 'Select * From ( ' From Dual
UNION ALL
Select 'UNION ALL select * from scott.EMP_BAK'||EMPNO||'' Name From scott.EMP
UNION ALL
Select ') Where Name = ''scott.EMP_BAK7788'' ' From Dual

I dont want to paste, then execute that script. For eaxmple lexical parameter
i.e.
Select * &' From scott.Emp'
should give result right away.