ÐAn important trend of current GIS development is to provide easy and effective access to spatial analysis functionalities for supporting decision making based on geo-referenced data. Within the framework of the ongoing SQL standards for spatial extensions, a spatial query language, called SQL/SDA, has been designed to meet such a requirement. Since the language needs to incorporate the importa...

The oracle database system is the large relation database management system which is applied most broadly at present. The PL/SQL language is a sort of block structured language, and it is the procedural language that the Oracle extends SQL, and it allows encapsulating operation logics, and its advantage is to use inscribed SQL sentence to define and realize 3GL language structure and describe m...

One weakness of SQL has been its inability to express certain classes of queries, e.g., iterative queries and database schema-independent queries. Fixes to this problem generally involve embedding SQL in a more expressive language. Re ection|the ability of a language to encode arbitrary programs and evaluate these encodings during execution|can provide a seamless, natural solution. In database ...

There is growing interest in query language extensions for pattern matching over event streams and stored database sequences, due to the many important applications that such extensions make possible. The push for such extensions has led DBMS vendors and DSMS venture companies to propose Kleene-closure extensions of SQL standards, building on seminal research that demonstrated the effectiveness...

The logic of nulls in databases has been subject of investigation since their introduction in Codd’s Relational Model, which is the foundation of the SQL standard. In the logic based approaches to modelling relational databases proposed so far, nulls are considered as representing unknown values. Such existential semantics fails to capture the behaviour of the SQL standard. We show that, accord...