CURRENT_USER
The niladic CURRENT_USER function returns a string of type "name" whose value represents a user name identification.
Data type "name" is a non-standard 31-character type for storing system identifiers.
Display CURRENT_USER
SELECT CURRENT_USER AS who_am_i; who_am_i ------------ jose
SQL92 specifies some additional niladic USER functions:
USER is a synonym for CURRENT_USER.
The SESSION_USER function returns the SQL-session user name.
The SYSTEM_USER function returns the database's initial default user.
A niladic USER function returns a SQL_TEXT character string whose value represents a user name.