Data definition languageIn the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures, especially database schemas. Common examples of DDL statements include CREATE, ALTER, and DROP. The concept of the data definition language and its name was first introduced in relation to the Codasyl database model, where the schema of the database was written in a language syntax describing the records, fields, and sets of the user data model.
Database theoryDatabase theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems. Theoretical aspects of data management include, among other areas, the foundations of query languages, computational complexity and expressive power of queries, finite model theory, database design theory, dependency theory, foundations of concurrency control and database recovery, deductive databases, temporal and spatial databases, real-time databases, managing uncertain data and probabilistic databases, and Web data.
Db4odb4o (database for objects) was an embeddable open-source object database for Java and .NET developers. It was developed, commercially licensed and supported by Actian. In October 2014, Actian declined to continue to actively pursue and promote the commercial db4o product offering for new customers. The term object-oriented database system dates back to around 1985, though the first research developments in this area started during the mid-1970s.
AmpersandThe ampersand, also known as the and sign, is the logogram , representing the conjunction "and". It originated as a ligature of the letters et—Latin for "and". The term ampersand is a corruption of and (&) per se and, which literally means "(the character) & by itself (is the word) and". The symbol & is derived from the ligature of ET or et, which is the Latin word for "and". Traditionally in English, when spelling aloud, any letter that could also be used as a word in itself ("A", "I", and, "O") was referred to by the Latin expression per se ('by itself'), as in "per se A" or "A per se A".
