CONCAT joins two expressions as a single character string. The data type of the return value is the same as the expressions, or if they are mixed, the one that results in a lossless conversion.
CHAR | NCHAR | VARCHAR2 | NVARCHAR2
char2 are text expressions.
CONCAT('The current date is ', 'October 13, 2006') returns the string
The current date is October 13, 2006.