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A temporal database stores data relating to time instances. It offers temporal data types and stores information relating to past, present and future time. Temporal databases can be uni-temporal, bi-temporal or tri-temporal. More specifically the temporal aspects usually include valid time, transaction time and/or decision time.
In temporal databases, transaction time is the time when some data has been loaded into a database. The time when a transaction is valid can be called the transaction time-period . It is a technical timeline controlled by a integration layer (for example a data warehouse ). [ 1 ]
Notably both of Oracle's implementations depend on the database's rollback segment and so only allow temporal queries against recent changes which are still being retained for backup. Microsoft SQL Server (version 2016) implements temporal tables with SYSTEM_VERSIONING. [13] MariaDB 10.3 implements system-versioned tables. [14]
In temporal databases, valid-time is the time period when an event happened or something was true in the real world, or more formally when a fact was valid in the modeled reality. The valid-time period is an interval based on event times, which are referred to as event datetime in data vault .
Short title: Microsoft SQL Server/Print version - Wikibooks, open books for an open world; Author: hbossot: Image title: File change date and time: 16:12, 10 January 2016
Bitemporal modeling is a specific case of temporal database information modeling technique designed to handle historical data along two different timelines. [1] This makes it possible to rewind the information to "as it actually was" in combination with "as it was recorded" at some point in time.
Time series datasets can also have fewer relationships between data entries in different tables and don't require indefinite storage of entries. [6] The unique properties of time series datasets mean that time series databases can provide significant improvements in storage space and performance over general purpose databases. [ 6 ]
A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.