SQL in a Nutshell, 3rd Edition

Built-in Scalar Functions

ANSI SQL built-in scalar functions identify both the current user session and its characteristics, such as the current session privileges. Built-in scalar functions are always nondeterministic. The CURRENT_DATE, CURRENT_TIME, and CURRENT_TIMESTAMP functions listed in Table 4-3 are built-in functions that fall into the date-and-time category of functions. Although the four platforms discussed in this book provide many additional functions beyond these SQL built-ins, the SQL standard defines only those listed in Table 4-3.

Table 4-3. ANSI SQL built-in scalar functions

Function	Usage
CURRENT_DATE	Returns the current date
CURRENT_TIME	Returns the current time
CURRENT_TIMESTAMP	Returns the current date and time
CURRENT_USER or USER	Returns the currently active user within the database server
SESSION_USER	Returns the currently active authorization ID, if it differs from the user’s ID
SYSTEM_USER	Returns the currently active user within the host operating system