SESAM/SQL is used for administering and processing user data structured in accordance with the relational model.
The relational model was originally formulated by E.F.Codd in 1970 on the basis of relational algebra and since then it has been both specified more precisely and expanded a number of times (e.g. in Codd “The Relational Model for Database Management Version 2”, 1990).
The principle characteristics of the relational model are as follows:
The relational model is characterized by the fact that the data structures are represented in the form of tables comprising rows (records) and columns. Logically, any relational database is made up of tables. The user sets up relationships between tables via the contents of the columns. This representation allows end users to understand the structure of a database intuitively.
Data manipulation in the relational data model is set-oriented, i.e. it is intended for use with sets of records and not with individual records. Even complex operations can be constructed from simple, set-oriented basic operations.
Relational database systems guarantee the logical and physical independence of data. Logical independence of data means that a user can create or modify his/her view of the data without changing the overall structure of the data. Existing programs need not be changed if new columns or tables are created. The deletion or modification of columns only means that those programs which access these columns need to be modified.
Physical independence of data means that the logical and physical structure of a database are independent of each other. Logical relationships between data structures can be formulated in terms of links between columns and require no specifications as to the internal storage structure of the database. Application programs need not be changed if the physical data structure is modified.
SESAM/SQL allows users to exploit fully these advantages of the relational model.