Transaction time

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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).{{cite news |title=A gentle introduction to bitemporal data challenges - Roelant Vos |newspaper=Roelant Vos |date=20 February 2023 |url=https://roelantvos.com/blog/a-gentle-introduction-to-bitemporal-data-challenges/}} More formally, it is the point-in-time during which a fact stored in the database is considered to be true.

The period is an interval based on load times (called load datetime in data vault{{cite web |access-date=2024-02-10 |title=Transactional Links - AutomateDV |url=https://automate-dv.readthedocs.io/en/latest/tutorial/tut_t_links/ |work=automate-dv.readthedocs.io}}), also called inscription timestamp. Other names of the interval is assertion timeline{{cite news |title=A not-so-gentle follow-up on bitemporal data challenges - Roelant Vos |newspaper=Roelant Vos |date=23 March 2023 |url=https://roelantvos.com/blog/a-not-so-gentle-follow-up-on-bitemporal-data-challenges/}}), state timeline) or technical timeline. SQL:2011 has support for transaction time through so-called system-versioned tables.{{cite web |access-date=2024-06-18 |date=2023-10-16 |language=en-us |surname=rwestMSFT |title=Temporal Tables - SQL Server |url=https://learn.microsoft.com/en-us/sql/relational-databases/tables/temporal-tables?view=sql-server-ver16 |work=learn.microsoft.com}}{{cite web |access-date=2024-06-18 |title=System-Versioned Tables |url=https://mariadb.com/kb/en/system-versioned-tables/ |work=MariaDB KnowledgeBase}}{{cite web |access-date=2024-06-18 |title=SAP Help Portal |url=https://help.sap.com/docs/SAP_HANA_PLATFORM/6b94445c94ae495c83a19646e7c3fd56/91302b26f62c4433bbc58e0a951cdc1d.html |work=help.sap.com}}{{cite web |access-date=2024-06-18 |language=en-us |title=System-period temporal tables |url=https://www.ibm.com/docs/en/db2/11.1?topic=tables-system-period-temporal |work=www.ibm.com}}

For many reasons, transaction time (when data arrives from a source system) is almost always different from valid time (when the event happened in the real world). For a data warehouse to unambiguously report what actually happened in the past it must be able to combine these two timelines. In bitemporal data models, valid-time and transaction time can be represented two-dimensionally in a Cartesian coordinate system. When data is delivered from the integration layer and is to be presented in a presentation layer (often in a dimensional model or wide table) it is often desirable to have the data on only one timeline.

In a database table, the transaction time is often represented as an interval allowing the system to "remove" entries by using two table-columns start_tt and end_tt. The time interval is closed [ at its lower bound and open ) at its upper bound.Kedar, S. V. (2013). Database management systems. Pune, India: Technical Publications. When the ending transaction time is unknown, it may be considered as until_changed. Academic researchers and some relational database management systems (RDBMS) have represented until_changed with the largest timestamp supported or the keyword forever. This convention is a technical workaround, and not technically precise.