Oracle SQL & PL/SQL

Column alias renames a column heading in a query. Its an alternate name for an exiting oracle object. The column alias is specified in the SELECT list by declaring the alias after the column name by using the space separator. Alias heading appears in UPPER casing by default. The alias should be declared in double quotes (“ “). Alias is declared after the column with minimum of one space. The AS keyword can be used between the column name and alias. An alias effectively renames the SELECT list item for duration of the query only. An alias cannot be used, any where in the SELECT list for operational purpose. Note  : Never consider Alias as a column Example :=          1)     Select 20 + 10 Mysum from dual;           2)    Select ename, sal salary, comm commission from emp;           3)    Select sal “Basic Salary” from emp;     ...