PostgreSQL supports the full set of SQL date and time types, shown in Table 8-9. The operations available on these data types are described in Section 9.9. Dates are counted according to the Gregorian calendar, even in years before that calendar was introduced (see Section B.4 for more information). Table 8-9. Date/Time Types Name Storage Size Description Low Value High Value Resolution timestamp [ (p) ] [ without time zone ] 8 bytes both date and time (no time zone) 4713 BC 294276 AD 1 micro

Table B-1 shows the tokens that are recognized as names of months. Table B-1. Month Names Month Abbreviations January Jan February Feb March Mar April Apr May June Jun July Jul August Aug September Sep, Sept October Oct November Nov December Dec Table B-2 shows the tokens that are recognized as names of days of the week. Table B-2. Day of the Week Names Day Abbreviations Sunday Sun Monday Mon Tuesday Tue, Tues Wednesday Wed, Weds Thursday Thu, Thur, Thurs Friday Fri Saturday Sat Table B

The date/time type inputs are all decoded using the following procedure. Break the input string into tokens and categorize each token as a string, time, time zone, or number. If the numeric token contains a colon (:), this is a time string. Include all subsequent digits and colons. If the numeric token contains a dash (-), slash (/), or two or more dots (.), this is a date string which might have a text month. If a date token has already been seen, it is instead interpreted as a time zone

Table 9-30 shows the available functions for date/time value processing, with details appearing in the following subsections. Table 9-29 illustrates the behaviors of the basic arithmetic operators (+, *, etc.). For formatting functions, refer to Section 9.8. You should be familiar with the background information on date/time data types from Section 8.5. All the functions and operators described below that take time or timestamp inputs actually come in two variants: one that takes time with time

Since timezone abbreviations are not well standardized, PostgreSQL provides a means to customize the set of abbreviations accepted by the server. The timezone_abbreviations run-time parameter determines the active set of abbreviations. While this parameter can be altered by any database user, the possible values for it are under the control of the database administrator — they are in fact names of configuration files stored in .../share/timezonesets/ of the installation directory. By adding or

Database roles are conceptually completely separate from operating system users. In practice it might be convenient to maintain a correspondence, but this is not required. Database roles are global across a database cluster installation (and not per individual database). To create a role use the CREATE ROLE SQL command: CREATE ROLE name; name follows the rules for SQL identifiers: either unadorned without special characters, or double-quoted. (In practice, you will usually want to add additio

Recall from Chapter 19 that the PostgreSQL server provides a large number of run-time configuration variables. You can set database-specific default values for many of these settings. For example, if for some reason you want to disable the GEQO optimizer for a given database, you'd ordinarily have to either disable it for all databases or make sure that every connecting client is careful to issue SET geqo TO off. To make this setting the default within a particular database, you can execute the

It is very difficult to enforce business rules regarding data integrity using Read Committed transactions because the view of the data is shifting with each statement, and even a single statement may not restrict itself to the statement's snapshot if a write conflict occurs. While a Repeatable Read transaction has a stable view of the data throughout its execution, there is a subtle issue with using MVCC snapshots for data consistency checks, involving something known as read/write conflicts. I

This module implements a data type cube for representing multidimensional cubes. F.9.1. Syntax Table F-3 shows the valid external representations for the cube type. x, y, etc. denote floating-point numbers. Table F-3. Cube External Representations External Syntax Meaning x A one-dimensional point (or, zero-length one-dimensional interval) (x) Same as above x1,x2,...,xn A point in n-dimensional space, represented internally as a zero-volume cube (x1,x2,...,xn) Same as above (x),(y) A one-dime

Before you can do anything, you must initialize a database storage area on disk. We call this a database cluster. (The SQL standard uses the term catalog cluster.) A database cluster is a collection of databases that is managed by a single instance of a running database server. After initialization, a database cluster will contain a database named postgres, which is meant as a default database for use by utilities, users and third party applications. The database server itself does not require