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In relational databases a virtual column is a table column whose value(s) is automatically computed using other columns values, or another deterministic expression. Virtual columns are defined of SQL:2003 as Generated Column, [1] and are only implemented by some DBMSs, like MariaDB, SQL Server, Oracle, PostgreSQL, SQLite and Firebird (database server) (COMPUTED BY syntax).
The nested set model is a technique for representing nested set collections (also known as trees or hierarchies) in relational databases.. It is based on Nested Intervals, that "are immune to hierarchy reorganization problem, and allow answering ancestor path hierarchical queries algorithmically — without accessing the stored hierarchy relation".
A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...
SRIDs are the primary key for the Open Geospatial Consortium (OGC) spatial_ref_sys metadata table for the Simple Features for SQL Specification, Versions 1.1 and 1.2, which is defined as follows: CREATE TABLE SPATIAL_REF_SYS ( SRID INTEGER NOT NULL PRIMARY KEY , AUTH_NAME CHARACTER VARYING ( 256 ), AUTH_SRID INTEGER , SRTEXT CHARACTER VARYING ...
A former Tennessee teacher who got pregnant after raping a 12-year-old boy pleaded guilty and has been sentenced to 25 years in prison with no parole. On Dec. 20, Alissa McCommon, 39, of Covington ...
Experts explain whether ice or heat for back pain will lead to better relief, and the best time to use each.
As Michael Hershey, R.D.N., points out: "demonizing seed oils has resulted in consumers overlooking actual key foundational [nutrition] components," such as eating enough fiber, protein, fruits ...
MySQL Workbench is the first MySQL family of products that offer two different editions - an open source and a proprietary edition. [31] The "Community Edition" is a full featured product that is not crippled in any way. Being the foundation for all other editions it will benefit from all future development efforts.