EJB Query Language

Hi All,
I am using SAP Netweaver Developer Studio(2004)version.I want to know that EJB2.0 Query Language will
support Joins,Internal select statement with in a select
statement or not.Is it posssible or not.I have a requirement lilke this,I have to use joins.
Thanks & Regards,
Guru

Guruvulu,
In EJB QL you may operate on objects relations (both 0..1 and 0..n) in the same way as with joins in SQL. So the answer is yes.
Read free <a href="http://www.theserverside.com/books/wiley/masteringEJB/downloads/MasteringEJB3rdEd.pdf">Mastering EJB</a> book -- it contains separate chapter on EJB QL.
Valery Silaev
EPAM Systems
http://www.NetWeaverTeam.com

Similar Messages

EJB query language help!!

Hi all, I have been trying to run a ejb query on JBoss 4.0.5, using built in hypersonic db, For some strange reasons am able to fetch all objects from db without any where clause but if am using a where clause with an attribute name from the entitybean am unable to retrieve any results.
I get an org.hibernate.QueryException, could not resolve property : "property name"
My ejb query looks like this...
SELECT template FROM TemplateSelect template WHERE template.template_name='Template_One'
TemplateSelect is my entity bean class and I do have an attribute named template_name in my bean class.
could any one please suggest me what could be wrong and also direct me to a good tutorial on ejb query language as well as I am fairly new to hibernate and ejb3 !
tons of thanks in advance!
pravin

Hi Anuradha ,
I'm afraid the query language does not support retrieving the date portion (i.e. truncating the time) from a date field.
I propose you turn you named into a BETWEEN query taking two parameters one for the beginning of the day and another for the end of the day. Then your named query could look like:
SELECT max(o.req_id) FROM requests o WHERE o.requestdate BETWEEN :start AND :end
The following code creates two calendar instances for the current day, one for 00:00:00 and another for 23:59:59:
Calendar start = Calendar.getInstance();
start.set(Calendar.HOUR_OF_DAY, 0);
start.set(Calendar.MINUTE, 0);
start.set(Calendar.SECOND, 0);
start.set(Calendar.MILLISECOND, 0);
Calendar end = Calendar.getInstance();
end.set(Calendar.HOUR_OF_DAY, 23);
end.set(Calendar.MINUTE, 59);
end.set(Calendar.SECOND, 59);
end.set(Calendar.MILLISECOND, 999);
Here is some sample code that creates a query instance for a named query called findMaxRequestPerDay and passes the Date of the above Calendar instance as actual parameter values. It assumes the named query is called findMaxRequestPerDay and the req_id field is a long:
Query query = em.createNamedQuery("findMaxRequestPerDay");
query.setParameter("start", start.getTime());
query.setParameter("end", end.getTime());
Long max = (Long)query.getSingleResult();
I hope this helps.
Regards Michael

Is EJB query language supports UNION

Hi All,
Can anyone suggest me is EJB query language supports UNION type of select queries
if possible can any one suggest me how to convert below Sql query to Ejb ql
Ex:
select * from table1 where id='10'
union all
select * from table1 where id='20'

The UNION clause specifies a combination of the output of two subqueries. The two queries must return the same number of elements and compatible types
1.You cannot use dependent value objects with UNION.
2.UNION ALL combines all results together in a single collection.
3.UNION combines results but eliminates duplicates.
4.If ORDER BY is used together with UNION, the ORDER BY
must refer to selection expression using integer numbers.
Example:
This example returns a collection of all employee objects of type EmpBean and all manager objects of type ManagerBean where ManagerBean is a subtype of EmpBean.
select e from EmpBean e union all select m from DeptBean d, in(d.mgr) mThis example shows a query that is not valid, because EmpBean and DeptBean are not compatible.
select e from EmpBean e union all select d from DeptBean d
Your Example:
Select e from Table1Bean e where e.id=10
union all
Select e from Table1Bean e where e.id=10

EJB Query Language where condtion based on date

Hi,
I am using EJB3 query language. In the table I have a column called requestdate which is in date time format. I have created an entity class.
I need to select few records using query language(named queries) based on this requestdate matching to the current date. I want to compare only based on Date value (truncating the time). Something like this
select max(o.req_id) from requests o where o.requestdate = :currentdate
currentdate is java.sql.Date value formatted to yyyymmdd only.
How can I do this using query language?
Please help to me get this done.
thanka
Anuradha

Hi Anuradha ,
I'm afraid the query language does not support retrieving the date portion (i.e. truncating the time) from a date field.
I propose you turn you named into a BETWEEN query taking two parameters one for the beginning of the day and another for the end of the day. Then your named query could look like:
SELECT max(o.req_id) FROM requests o WHERE o.requestdate BETWEEN :start AND :end
The following code creates two calendar instances for the current day, one for 00:00:00 and another for 23:59:59:
Calendar start = Calendar.getInstance();
start.set(Calendar.HOUR_OF_DAY, 0);
start.set(Calendar.MINUTE, 0);
start.set(Calendar.SECOND, 0);
start.set(Calendar.MILLISECOND, 0);
Calendar end = Calendar.getInstance();
end.set(Calendar.HOUR_OF_DAY, 23);
end.set(Calendar.MINUTE, 59);
end.set(Calendar.SECOND, 59);
end.set(Calendar.MILLISECOND, 999);
Here is some sample code that creates a query instance for a named query called findMaxRequestPerDay and passes the Date of the above Calendar instance as actual parameter values. It assumes the named query is called findMaxRequestPerDay and the req_id field is a long:
Query query = em.createNamedQuery("findMaxRequestPerDay");
query.setParameter("start", start.getTime());
query.setParameter("end", end.getTime());
Long max = (Long)query.getSingleResult();
I hope this helps.
Regards Michael

Object Query Language (OQL) Support ?

I know Toplink has an "ExpressionBuilder" type querying
But does Toplink support Object Query Language (OQL)
Example :
Something like this ?
// perform query
OQLQuery query = new OQLQuery(
"select x from Person x where x.name = \"Doug Barry\"");
Collection result = (Collection) query.execute();
Iterator iter = result.iterator();
Thanks
Ratheesh

Ratheesh,
TopLink does not support OQL. We offer query support through the following 5 options:
1. EJB QL - for both Entity Beans (CMP/BMP) and Java objects
2. TopLink Expressions - Object based query API
3. SQL calls
4. Stored procedure calls
5. Quey by example
Doug

PLS HELP ! WLS 6.1 CMP ejb query ORDERBY clause

Please Help,
How to do OrderBY clause ASC and DESC in weblogic 6.1 CMP?
Thanks

Hi Deepak,
First of all, thanks for answering.
Do you mean I should place that query within "weblogic-query" tag in the weblogic-cmp-rdbms-jar.xml?
I tried comment the query part in ejb-jar.xml with the ammended weblogic-cmp-rdbms-jar.xml.
The ejb compiler fail to compile the ejb because it cannot find the coresponse
Method.
Can you state a simple example this case with descriptors?, the descriptor make
me headache. Thanks
Deepak Vohra <[email protected]> wrote:
The WebLogic Query Language extension, ORDERBY, is a keyword that works
with the Finder method to allow you to specify which CMP file you want
to use for your selections.
The following example shows the use of the extension, ORDERBY.
SELECT A from A for Account.Bean
ORDERBY A.id ASC | DESC
ASC | DESC
Specify whether the ordering sequence is ascending or descending. ASC
is the default.
Ray wrote:
Please Help,
How to do OrderBY clause ASC and DESC in weblogic 6.1 CMP?
Thanks

Applying a query language to collections

Hi, we handed in a project a while ago that was essentially to read in data from a .DAT file, store it in appropriate collections, then use a basic query language to filter through the stored data. I wasn't really happy with my querying though, as it was basically a huge succession of control statements. The queries were of the form "select OBJECTNAME where ATRIBUTE OPERATOR VALUE and ATRIBUTE OPERATOR VALUE", there could be as many sub clauses as desired (0... 200 whatever). For example "select elephant where height > 360 and weight <= 1000".
We had a comment back that we should use a Query interface and a two subclasses to represent a simple query (e.g. height > 360) and then a conjunctive query (ie simplequery1 AND simplequery2 ). The Query interface would then have a match method. I'm struggling to get my head around how I do this, does anyone have a simple example or explaination that might help me out?
Cheers.

I've done something like this a couple times. Your need to get a better idea of what you want your query language to look like. For example, if you're given a list of elephants, the "select elephant" part is unnecessary (your query will just return a list of matching elephants). You should decide if you want it to handle things like (height > (weight / 2)), whether conditions can be nested "((a and b) or (c and d)) and (e or f)". Will you need to support the conditional operator (a ? b : c) or a unary operator (-)? How complex will your order of operations rules be?
If you keep it simple (always two operands), you could go with something like this:
public interface QueryOperator
public boolean eval(Object leftParam, Object rightParam);
public enum BasicOperators implements QueryOperator
public class QueryElement
private QueryOperator operator;
private Object leftParam;
private Object rightParam;
}

XPath Query Language Reference

Aside from the three little examples given in the 11g Guide and the B2B Tech Note #011, is there a reference available for the XPath Query Language used by B2B? Is is possible to use complex XPath queries in the B2B Doc Definitions?

I'm mainly just looking for the full capabilities of the queries.
Specifically, at the moment, I'm looking for a way to match the value of a node to a group of values (like a sql 'in') as well as check the existence and value of other nodes within the same query.
Do the documents I find for 'Preference XPath' pertain here?

Query language for CTXRULE MATCHES

I am trying to build an alerting application when, on receipt of a new XML document, user's are alerted if the document matches one or more of the profiles that they have defined. I have created a CTXRULE index that does this but only with very simple profiles. For example ABOUT(soccer), which is the example in the Text documentation.
Is it possible to create more complex queries, for example using WITHIN to only match within defined elements of the XML document. Is there a definition of the query language that can be used with MATCHES and are there any good example?
Thanks
Martin Haigh

Omar,
Thanks for the reply. I had actually found that document myself but I couldn't get the WITHIN clause to work and that document conflicted with the ORACLE documentation at:
<a href="http://download-west.oracle.com/docs/cd/B10501_01/text.920/a96517/ind.htm#1010647> Do you have any examples of using WITHIN?
Thanks
Martin

Query language for XML documents

Which is a better (efficiency in terms of memory management) query language for interacting with XML documents.The query language shouls support 'insert', 'delete', 'update' and 'select' commands. How fast is database as compared to XML ( database being replaced by XML) when only 'insert' n 'select' commands are issued?

Hi,
I suggest you use the Sunopsis JDBC for XML driver that will let you perform all kind of SQL statements on your XML files. It is a type 4 driver so it's very use to use. You may have more information and download it here:
http://www.sunopsis.com/corporate/us/products/jdbcforxml/
Hope that will help
Simo Fernandez

Query language for XML that is going to remove use of database

Friends,
I want to know whether my idea is feasible or not.
I want to make a query language similar to SQL for XML which is going to remove the need for database for a large extent.
Their will be queries for making table,extracting data,making foreign key all through XML and no database.
I just want to know that is their any market value for such a project and will it be sellable,so that i can start working on it.

There is no way to judge any future market for such a thing.
As it is, XML is widely abused, having mutated from its original purpose, a markup language readable by both machine and human, to a general data interchange language. It winds up being extremely slow and convoluted, in some cases overwhelming the hardware when a simple and common error occurs, then having to catch up. A big part of this is the silly and redundant method of defining metadata, again and again and again and again.
So what you want to do is create a database which will be highly formatted with redundant information, dynamically. This is silly, why does data need to be stored in a human readable format? It doesn't always even need to be presented in a human readable format! Why the heck would you need to read the bits of an mp4? Steganography?
What you are proposing is the exact opposite of what is needed. What is needed is a way to describe metadata for many different kinds of data, in a manner that can be interpreted by both man and machine at appropriate times, extensible for various paradigms.
What can be sold, on the other hand, is another question entirely, and not technical at all.
First definition of database that pops up during a search: an organized body of related information
Why would you want to get rid of that?

JPA query language syntax

My question is if JPA query language syntax allows full qualified class names in the SELECT clause of the query, e.g.:
SELECT * FROM com.abc.Person
This works well with Hibernate, but TopLink Essentials complains about the dots in com.abc.Person.
In the Java EE 5 Tutorial only partially qualified names ( SELECT * FROM Person) are used.
There are only examples with fully qualified names for constants in WHERE clauses.

my first guess:
SELECT t FROM tablename t WHERE t.timestamp>:somethingwhere :something
is handled with something like: (..).setParameter("something", someSQLDate);

SAP Query Language max retrieve size 512 bytes?

Hello,
Does anyone know if there is a 512 byte limit on retrieves from a table when using SAP Query Language? In other words the length of all the fields in the retrieve can't exceed 512 bytes?
Thanks

Hi,
And also you need check this thread
May this will help you out.
a®

EJB Query Problem

Hi All,
I`m using jdeveloper 11g and I have an EJB query select distinct substr(o.hostName, 1,10) from Host o where o.hostName like :searchPrefix
When i run this query I get this error message
javax.persistence.PersistenceException: Exception [EclipseLink-8024] (Eclipse Persistence Services - 1.2.0.v20091016-r5565): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Syntax error parsing the query [Host.distinctVlid: select distinct substr(o.hostName, 1,10) from Host o where o.hostName like :searchPrefix], line 1, column 22: syntax error at [(].
Internal Exception: MismatchedTokenException(81!=32)
Is it forbidden to use substr or distinct in ejb querys?

Hi Pedja,
I have tried to use your suggestion and created this method
public List<String> getHostVlidSuggestion(Object searchPrefix) {
Query query = em.createQuery("select distinct substring(o.hostName, 1, 10) as hostName from Host o where o.hostName like :searchPrefix");
query.setParameter("searchPrefix", searchPrefix);
query.setMaxResults(10);
return query.getResultList();
Now I`m getting this error
Exception [EclipseLink-6088] (Eclipse Persistence Services - 1.2.0.v20091016-r5565): org.eclipse.persistence.exceptions.QueryException
Exception Description: There are no attributes for the ReportQuery.
     at org.eclipse.persistence.exceptions.QueryException.noAttributesForReportQuery(QueryException.java:815)
     at org.eclipse.persistence.queries.ReportQuery.prepare(ReportQuery.java:1032)
     at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:464)
     at org.eclipse.persistence.queries.ObjectLevelReadQuery.checkPrepare(ObjectLevelReadQuery.java:732)
     at org.eclipse.persistence.queries.DatabaseQuery.prepareCall(DatabaseQuery.java:1572)
     at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:207)
     at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:141)
     at org.eclipse.persistence.in
Got any idea?
Edited by: Azzaiel on Jun 2, 2010 6:43 PM

Limit query for Java Persistence Query Language

Hi,
Anybody know Java Persistence Query Language can support limit querry to limit the number of row return(Like SQL LIMIT clause)?
Thanks

I think the javax.persistence.Query methods setFirstResult and setMaxResults are what you need...

EJB Query Language

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