A Period literal is used to specify a period constant. It has the form of the PERIOD keyword followed by a quote string in a specific format. The element type of a period literal is derived from the format of the DateTime values specified in the quoted string. The general format of period literals is:
Date literal: PERIOD ‘(2005-02-03, 2006-02-04)’
Time literal: PERIOD ‘(12:12:12.340000, 13:12:12.340000)’
Note that the character representation of a period value from the database includes single quotes around the elements and can therefore not be directly used in the construction of a literal.