CQL Sample Clauses

CQL. CQL is syntactically very similar to the SELECT statement of SQL making it easy to learn and understand for users who have had previous experience of SQL-like languages. Furthermore, being a declarative language, it leaves all choices of how to execute and optimize the query to the DSMS. A dominating part of the data manipulation of a CQL query is performed by relation-to- relation operators [3]. The operators include many of those normally found in SQL, such as projection, selection, aggregation, joining, grouping, etc. This approach was chosen so that well understood relational concepts could be reused and extended. Beyond SQL, CQL has stream-to-relation and relation-to-stream operators which, as their names suggest, convert from streams to relations and vice versa. Together with the relation- to-relation operators of SQL they offer flexibility in how data can be manipulated. Once a stream-to-relation operator has been applied to a stream it can be subjected to regular relation- to-relation operators after which it may be, if necessary, transformed back to a stream using a relation-to-stream operator.