I am using Google App Engine for a project and I need to do some queries on the database. I use the JDOQL to ask the database. In my case I want to obtain the university that contains the substring "array". I think my query has a mistake because it returns the name of universities in the alphabetical order and not the ones containing the substring.
Query query = pm.newQuery("SELECT FROM " + University.class.getName() + " WHERE name.contains("+array+") ORDER BY name RANGE 0, 5");
Could someone tell me what's wrong in my query?
Thank you for your help!
EDIT
I have a list of universities store and I have a suggestbox where we can request a university by his name. And I want to autocomplete the requested name.
App engine does not support full-text searches, you should star issue 217. However, A partial workaround is possible. And in your case I think it is a good fit.
First thing, adjust your model such that there is a lower (or upper case) version of the name as well -- I will assume it is called lname. Unless you want your queries to be case-sensitive.
Then you query like this:
Query query = pm.newQuery(University.class);
query.setFilter("lname >= startNameParam");
query.setFilter("lname < stopNameParam");
query.setOrdering("lname asc");
query.declareParameters("String startNameParam");
query.declareParameters("String stopNameParam");
query.setRange(0, 5);
List<University> results = (List<University>) query.execute(search_value, search_value + "z");
The correct way to do this is like this -
Query query = pm.newQuery(University.class,":p.contains(name)");
query.setOrdering("name asc");
query.setRange(0, 5);
List univs = q.execute(Arrays.asList(array));
(note- In this case the :p is an implicit param name you can replace with any name)
Related
I'm struggling with making order parametrised. The best would be to have
... order by :orderColumn :orderDirection ...
Is it even possible to turn:
#Query("select * from Document where folderId = :folderId AND documentType = :documentType"
+ " order by created desc limit :limit")
List<Document> findByFolderIdAndDocumentTypeOrderByWithLimit(Long folderId, String documentType,
String orderColumn, Integer limit);
Into:
#Query("select * from Document where folderId = :folderId AND documentType = :documentType"
+ " order by :orderColumn desc limit :limit")
List<Document> findByFolderIdAndDocumentTypeOrderByWithLimit(Long folderId, String documentType,
String orderColumn, Integer limit);
I'm using spring-data-jdbc 1.1.3.REELASE version. Even doing it for just column name would help me a lot.
Replacing a column name with a bind parameter is not possible.
This is a limitation of JDBC, and possibly even of SQL.
What you can do is use an expression that evaluates to the value of different columns based on a bind parameter.
Something like
... ORDER BY CASE
WHEN :orderColumn = 'created' THEN created
WHEN :orderColumn = 'updated' THEN updated
WHEN :orderColumn = 'deleted' THEN deleted
ELSE 1
END;
Note that this kind of constructed isn't well supported by query optimisers and therefore will not utilise any index that would otherwise apply.
If you require better support by the optimiser you can always write a custom query that you create dynamically.
If you decide to do so, make sure you do not incorporate Strings from untrusted sources in your SQL statement to avoid SQL injection vulnerabilities.
Use the PagingAndSortingRepository
#Query("select * from Document where folderId = :folderId AND documentType = :documentType")
List<Document> findByFolderIdAndDocumentTypeOrderByWithLimit(Long folderId, String documentType, Pageable pageable);
And call the method:
findByFolderIdAndDocumentTypeOrderByWithLimit(1,"Type", PageRequest.of(0, <limit>, Sort.by(<column name>).descending());
sume examples you can fine here
Until there will be version of spring-data-jdbc (as far as I know 2.X.X.RELEASE) supporting Pagable object I've decided for this particular case use NamedParameterJdbcTemplate and tail my own query. I hope this or other answers here will help someone. Thank you for your help :)
I have a MemoryIndex created like this.
```
Version version = Version.LUCENE_47;
Analyzer analyzer = new SimpleAnalyzer(version);
MemoryIndex index = new MemoryIndex();
index.addField("text", "Readings about Salmons and other select Alaska fishing Manuals", analyzer);
```
Then, I have a query containing a number of sub-query which is created from a set of concepts (including id, name, description). Right now I have to loop for every concept, generate a query, and finally check if it is matched => if it is, I append it to a string which is used to store matches
```
for (Concept concept : concepts) {
Query query = queryGenerator.getQueryForConcept(concept);
float score = query != null ? index.search(query) : 0.0f;
if (score > 0) {
matches.append(sep + concept.getId() + "|" + concept.getName());
sep = "|";
}
}```
The problem is: the number of concepts is growing larger and larger, which affects the performance. Is there anyway that I can create a one single query and compare to a document, and find out what concepts have been hit the document?
I tried using BooleanQuery as a whole, then add all subquery which derrived from concept into it. It matches but don't know which subquery hits, and even if we do, how do we put the details like "id", and "name" of a concept into it?
Much appreciate all answers
How do you implement automatically generated database (let it be SQL) requests?
Let us have offline shop with filters:
The database is standalone offline.
SO if I want to filter items by Price the request would be something like:
select Snowboard.Name
from Snowboard
where Snowboard.Price between 400 and 600;
And if I filter by two characteristics e.g. Price from and Camber. There would be:
select s.Name, s.Camber
from Snowboard s
where s.Price between 400 and 600
and s.Camber in ('Rocker', 'Hybrid');
The question is how could it be implemented in Java so that these requests are generated automatically from any combination of filters selected?
Quick and dirty solution #1
Generate a query at run time & make clever use of WHERE 1=1 condition as the number of where clause are unknown. (This sample is in C# but works more or less the same with JAVA as well)
string sql= #"select Snowboard.Name
from Snowboard
where 1=1";
Now you can build your query based on the UI element selections like
string whereClause="";
if(yourCheckBoxPrice.Checked)
{
whereClause+= " AND Price BETWEEN "+ txtPriceFrom.Text + " AND "+ txtPriceTo.Text;
}
if(yourCheckBoxCamber.Checked)
{
whereClause+= " AND Camber IN ("+ /* your list of values go here */ +")";
}
sql += whereClause;
2nd Solution (Use SQL CASE)
You can use SQL CASE inside your query for each where clause to check for nulls or specific values. But beware, dynamic SQL will make your code pretty messy & hard to read (Can be done via a stored procedure as well)
SQL- CASE Statement
I advise you to use a stored procedure with a mix of both options 1 and 2. Implementing Dynamic SQL Where Clause. Keep it simple and you are good to go.
I am new to hibernate and still learning the basics. I'd appreciate if someone can point me in the right direction.
I have a class:
Destination
id
name
longitude
latitude
I can read destinations based on id with something like this:
List result = session.createQuery("from Destination as d where d.id=2").list();
However, I want to read destinations from database using name. I can perhaps write something like this as a query:
String name; // name set somewhere else, say a function argument
List result = session.createQuery("from Destination as d where d.name LIKE %"+name).list();
I believe this will yield all destinations with names similar to (variable) name.
Is there something inbuilt in hibernate for such use cases or is there a better way to handle this ?
EDIT:
One thing that follows from my thought process is: name column on destination db table will have an index setup. Can I map this index in some way to the Destination class using hibernate ?
You could build your query by concatenating strings. A more elegant solution would be to use the Hibernate Criteria API.
You query would then look something like:
List result = session.createCriteria(Destination.class)
.add(Restrictions.like("name", "%" + name)
.list();
Hello guys I am having some problems with exact matches while doing a NamedQuery.
I am currently using something like this:
#NamedQuery(name = MyClass.GET_ENTRY_BY_NAME, query = "select e from Entry e where e.name =:"+ Entry.NAME )
...
Query query = em.createNamedQuery(MyClass.GET_ENTRY_BY_NAME);
query.setParameter(Entry.NAME, myEntry.getName());
It works for most cases, however I noticed that in case the user pass the file name with an space at the end, the namedQuery ignores that character. For example:
Query query = em.createNamedQuery(MyClass.GET_ENTRY_BY_NAME);
query.setParameter(Entry.NAME, myEntry.getName()+ " ");
Will return the same result as the query before. Bypassing my 'valid entry' validation. In other words I'd like the query to return no entry at all and treat the error later on.
One workaround I could think of, is to put single quotes surrounding my parameter in the namedQuery, like this:
#NamedQuery(name = MyClass.GET_ENTRY_BY_NAME, query = "select e from entry e where e.name =':"+ Entry.NAME "'")
However it will trash my code in case the String contains single quotes in it...
Any ideas guys?
I guess this happens because your database field is declared as CHAR(...), and therefore stored values are padded with whitespaces which are not taken into account by = operation.
So, you may either declare your database field as VARCHAR(...) or use a built-in trim function:
query = "select e from Entry e where trim(trailing from e.name) =:"+ Entry.NAME
I did some research in JPA and found out that it does some automatic trimming for CHARs, I am not sure if this behaves the same with Strings, but since it is happening to me... I believe so. The only way to bypass it is by setting some attribute within the session DatabaseLogin object (see http://www.eclipse.org/eclipselink/api/1.1/org/eclipse/persistence/sessions/DatabaseLogin.html#setShouldTrimStrings) .
Well I didn't want to be messing up with the session properties so I decided to make some sort of check and throwing the same exception as the NoResultException catch does in my code.
I basically took the result from the database and compared the field with the String I used:
query.setParameter(Entry.NAME, myEntry.getName());
...
if(!StringUtils.equals(result.getName(), myEntry.getName()){
do a cool throw just like NoResultException Catch
}
I also had to include the Trim function axtavt! This is just to make sure that if the database has a column with trailing spaces and it matches the parameter given by the user, it will be included as a valid answer. For example:
Database entry: Name = "Flavio " - Trimmed with Function = "Flavio".
Parameter passed: Name = "Flavio " - Trimmed by JPA automatic function = "Flavio".
If it isnt trimmed at all it will just Compare "Flavio " with "Flavio", returning NoResult when it was supposed to return that Entry.
Nasty workaround, but as long as there is no other way to stop the auto-trimming we will have to just make use of this sort of things.
Thanks for all the other answers!!