LIKESIMILAR TO Regular ExpressionsEXTRACT, date_partdate_truncPostgreSQL provides a large number of functions and operators for the built-in data types. Users can also define their own functions and operators, as described in Part V. The psql commands \df and \do can be used to list all available functions and operators, respectively.
If you are concerned about portability then note that most of the functions and operators described in this chapter, with the exception of the most trivial arithmetic and comparison operators and some explicitly marked functions, are not specified by the SQL standard. Some of this extended functionality is present in other SQL database management systems, and in many cases this functionality is compatible and consistent between the various implementations. This chapter is also not exhaustive; additional functions appear in relevant sections of the manual.