Oracle PL/SQL Programming, 6th Edition

Chapter 10. Dates and Timestamps

Most applications require the storage and manipulation of dates and times. Dates are quite complicated: not only are they highly formatted data, but there are myriad rules for determining valid values and valid calculations (leap days and years, daylight saving time changes, national and company holidays, date ranges, etc.). Fortunately, the Oracle database and PL/SQL provide a set of true datetime datatypes that store both date and time information using a standard internal format.

For any datetime value, the database stores some or all of the following information:

• Year

• Month

• Day

• Hour

• Minute

• Second

• Time zone region

• Time zone hour offset from UTC

• Time zone minute offset from UTC

Support for true datetime datatypes is only half the battle. You also need a language that can manipulate those values in a natural and intelligent manner—as actual dates and times. To that end, Oracle provides you with support for SQL standard interval arithmetic, datetime literals, and a comprehensive suite of functions with which to manipulate date and time information.

Datetime Datatypes

For a long time, the only datetime datatype available was DATE. Oracle9i Database shook things up by introducing three new TIMESTAMP and two new INTERVAL datatypes, offering significant new functionality while also bringing Oracle into closer compliance with the ISO SQL standard. I’ll talk more about the INTERVAL datatypes later in this chapter. The four datetime datatypes are:

DATE

Stores a date and ...