EJB QL
EJB QL or EJB-QL ( Enterprise Java Beans Query Language ) is a query language for Enterprise Java Beans (EJB). It is used in J2EE applications. Compared to SQL , it is less complex, but also not as powerful.
history
In particular EJB3 QL was the query language of Hibernate , influenced, Hibernate Query Language HQL.
Differences from SQL
The syntax of the EJB QL is similar to that of SQL. The queries used differ from the relational language SQL, which is based on the relational model. Instead, EJB QL uses the so-called "abstract scheme" of the Enterprise Java Beans. An SQL query contains tables as well as their rows and columns. In contrast to this, the EJB-QL queries contain EJBs, as well as their persistent states and relations. The result of an SQL query are rows with a fixed number of columns. The result of an EJB-QL query are objects of a specific class or a collection of values that were retrieved from a CMP field.
swell
- ↑ See Introduction (p. 4) in " expert one-on-one: J2EE Design and Development ", (c) 2002 wrox press.
- ↑ Chapter 7. EJB-QL: The Object Database Query Language
- ↑ ADVANCED EJB QL: SQL vs. EJB QL: Relational and Object Database Query Languages ( Memento from April 12, 2009 in the Internet Archive )