Network Deployment (Distributed operating systems), v8.0 > Reference > Developer best practices
EJB query language limitations and restrictions
When using the EJB query language on the product, deviations can be seen in comparison to standard EJB query language. The limitations and restrictions be aware of are listed in the following section.
This topic outlines current known limitations and restrictions.
- EJB query language (QL) queries involving enterprise beans with keys made up of relationships to other enterprise beans appear as not valid and cause errors at deployment time. This is a known problem.
- The IBM EJB QL support extends the EJB 2.0 specification in various ways, including relaxing some restrictions, adding support for more DB2 functions, and so on. If portability across various vendor databases or EJB deployment tools is a concern, then care should be taken to write all EJB QL queries strictly according to Chapter 11 in the EJB 2.0 specification.
- Pre-loading across m:n relationships results in the generation of inaccurate structured query language (SQL). This is a known limitation that may be addressed in the future.
- Pre-loading across self referencing relationships causes inaccurate SQL to be generated.
- Avoid relationships between parent and children enterprise beans within the same inheritance hierarchy that are not well-defined.
- EJB Query Language validation for EJB 2.0 JAR files currently runs as a part of the EJB-RDB Mapping validation. If a mapping document (Map.mapxmi file) does not exist in the project, the EJB queries are not validated.
EJB query language
Use EJB query