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Valid time is the time for which a fact is true in the real world. In the example above, the Person table gets two extra fields, valid_from and valid_to, specifying when a person's address was valid in the real world. On 1975-04-04, John's father proudly registered his son's birth.
A language that supports the statement construct typically has rules for one or more of the following aspects: Statement terminator – marks the end of a statement; Statement separator – demarcates the boundary between two statements; need needed for the last statement; Line continuation – escapes a newline to continue a statement on the ...
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
SQLAlchemy was first released in February 2006. It has evolved to include a wide range of features for database interaction and has gained popularity among Python developers. Notable versions include: Version 0.1 (2006): [5] Initial release. Version 1.0 (2015): [6] Major enhancements in ORM and SQL expression language.
An SQL select statement and its result. In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data.
The valid time and transaction time do not have to be the same for a single fact. For example, consider a temporal database storing data about the 18th century. The valid time of these facts is somewhere between 1701 and 1800. The transaction time would show when the facts were inserted into the database (for example 1998-01-21).
Added SQL-standard SEARCH and CYCLE clauses for common table expressions, allow DISTINCT to be added to GROUP BY [173] [174] 15 2022-10-13 15.10 2024-11-21 2027-11-11 Implements SQL-standard MERGE statement. PL/Python now only supports current Python 3, and plpythonu now means Python 3, no longer the discontinued Python 2.