EJB QL or EJB-QL is a portable
database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases ...
query language
Query languages, data query languages or database query languages (DQL) are computer languages used to make queries in databases and information systems. A well known example is the Structured Query Language (SQL).
Types
Broadly, query language ...
for
Enterprise Java Beans
Jakarta Enterprise Beans (EJB; formerly Enterprise JavaBeans) is one of several Java APIs for modular construction of enterprise software. EJB is a server-side software component that encapsulates business logic of an application. An EJB web c ...
. It was used in
Java EE
Jakarta EE, formerly Java Platform, Enterprise Edition (Java EE) and Java 2 Platform, Enterprise Edition (J2EE), is a set of specifications, extending Java SE with specifications for enterprise features such as distributed computing and web ser ...
applications. Compared to SQL, however, it is less complex but less powerful as well.
History
The language has been inspired, especially EJB3-QL, by the native Hibernate Query Language
HQL.
In EJB3 It has been mostly replaced by the
Java Persistence Query Language.
Differences
EJB QL is a database query language similar to SQL. The used queries are somewhat different from relational SQL, as it uses a so-called "abstract schema" of the enterprise beans instead of the relational model. In other words, EJB QL queries do not use tables and their components, but enterprise beans, their persistent state, and their relationships. The result of an SQL query is a set of rows with a fixed number of columns. The result of an EJB QL query is either a single object, a collection of entity objects of a given type, or a collection of values retrieved from
CMP fields. One has to understand the data model of enterprise beans in order to write effective queries.
See also
*
HQL
*
SQL
References
{{DEFAULTSORT:Ejb Ql
Information science
Query languages