Search results
Results from the WOW.Com Content Network
In addition to basic equality and inequality conditions, SQL allows for more complex conditional logic through constructs such as CASE, COALESCE, and NULLIF. The CASE expression, for example, enables SQL to perform conditional branching within queries, providing a mechanism to return different values based on evaluated conditions. This logic ...
IMAGE is a database management system (DBMS) developed by Hewlett-Packard and included with the HP 3000 minicomputer. It was the primary reason for that platform's success in the market. It was also sometimes referred to as IMAGE/3000 in its initial release, and later versions were known as TurboIMAGE, and TurboIMAGE/XL after the PA-RISC migration.
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".
In the context of information retrieval, QBE has a somewhat different meaning. The user can submit a document, or several documents, and ask for "similar" documents to be retrieved from a document database [see search by multiple examples [2]]. Similarity search is based comparing document vectors (see Vector Space Model).
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 ...
This is an important element of SQL. Statements, which may have a persistent effect on schemata and data, or may control transactions, program flow, connections, sessions, or diagnostics. SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
An example of a database that has not enforced referential integrity. In this example, there is a foreign key ( artist_id ) value in the album table that references a non-existent artist — in other words there is a foreign key value with no corresponding primary key value in the referenced table.