The CONCAT function returns the concatenated value expressions.
    The result is a VARCHAR type large enough to hold all source
    value expressions.

    Any date/time or numeric values are implicitly converted to
    VARCHAR types prior to concatenation. For dialects ORACLE LEVEL1
    and ORACLE LEVEL2, any supplied value that is NULL is ignored.
    For all other dialects, in conformance with the ANSI and ISO SQL
    database language standard, the resulting CONCAT expression is
    NULL.

    CONCAT is functionally equivalent to the concatenation operator
    (||).

    Example: Using the CONCAT function

    SQL> select distinct CONCAT (e.last_name, ' has a ', d.degree, ' degree')
    cont> from employees e, degrees d
    cont> where e.employee_id = d.employee_id
    cont> limit to 5 ROWS;

     Ames          has a MA  degree
     Ames          has a PhD degree
     Andriola      has a MA  degree
     Andriola      has a PhD degree
     Babbin        has a MA  degree
    5 rows selected