I'm trying to select a sequence id from the database using this query:
#Query("select max(pi.sequence) + 1 from ProductImage pi where pi.product = :product")
int nextSequenceForProduct(#Param("product")Product product);
It works well except when there's no values in the table, it throws some type of null value exception from the JPA code.
Is there a way to handle null values in spring jpa? For example something like this SQL:
select ifnull(max(pi.sequence),1) from ....
you can use nvl() function and change the query to native query or named native query to avoid the exception
#NativeQuery("select nvl(max(pi.sequence),0) + 1 from ProductImage pi where pi.product = :product")
Related
I have a spring-boot project with Spring-Data. I want to do a query like:
SELECT * FROM my_table WHERE column_1 = column_2
How can I do it using the SpringData JpaRepository? I tried to find a way like:
MyTable findByColumn1...Column2() without any luck
There is no default way to do that you have to use the #Query annotation like this:
#Query("select e from entity e where e.column1 = e.column2")
List<Entity> findByColumn1EqualsColumn2();
If you wanna use default method only you can use
List<Entity> findByColumn1AndColumn2(#Param("column1") String column1, #Param("column2") String column2);
And then passing the same parameter for column1 and column 2
i.e.
String column= "abc";
List<Entity> entitylist=repository.findByColumn1AndColumn2(column,column);
I have the following named query
#NamedQuery(name = "UserFlight.getUserFlightDetails",
query = "SELECT new com.foobar.UserFlightDetails(uf.flight.divertedAirport, uf.flight.number) " +
"FROM UserFlight uf WHERE uf.user.id=?1 AND uf.flight.id=?2")
The UserFlightDetails constructor is as follows
public UserFlightDetails(Airport airport, String flightNumber) {
this.setDivertedAirport(airport);
this.setFlightNumber(flightNumber);
}
divertedAirport is a foreign key in the flight table, path=(uf.flight.divertedAirport)
My problem is when divertedAirport is null (it's a nullable foreign key), my HQL query returns null as the result (The code doesn't even trigger the constructor above), so I don't get the flightNumber which is never null.
If the divertedAirport isn't null, I get both the airport and the flight number fine (and the above constructor gets executed just fine).
What could be causing this and how could I resolve it? I tried some null functions like nullif and coalesce but nothing helped.
I'm using spring boot 1.2.7, hibernate-core 4.3.11.Final
Probably, the problem is the uf.flight.divertedAirport. This expression do a JOIN between flight and divertedAirport but, as you say, divertedAirport is a fk and can be null.
So, you need to use the LEFT JOIN.
I would rewrite your query like this:
#NamedQuery(name = "UserFlight.getUserFlightDetails",
query =
"SELECT new com.foobar.UserFlightDetails(divertedAirport, flight.number)
FROM UserFlight uf
JOIN uf.flight flight
LEFT JOIN flight.divertedAirport divertedAirport
JOIN uf.user user
WHERE user.id = ?1 AND flight.id = ?2 ")
I remove the references like uf.user.id for a explicit JOIN (JOIN uf.user user plus user.id), because is more legible and this kind of problem that generated your question is more easy to find using this way to write JPQL queries.
Let say I have the following sql table. Customer_id column is a primary key with smallint.
And I am trying to create a linq query, where I want to get all data for customer with id, let say 1.
How to do this.
Already done and not working:
1.
var query = from row in dt.AsEnumerable()
where row.Field<Int32>("customer_id") == Convert.ToInt32(2)
select row;
2.
var query = from row in dt.AsEnumerable()
where row.Field<Int16>("customer_id") == Convert.ToInt16(2)
select row
debug for example 1,2
Syntax error
Exceptions
Why don't you use this:
DataRow needle = hayStack.Tables["Customer"].Rows.Find(2);
Your method should be rewritten as something like this:
private DataRow GetCustomerDetails(Int16 customer_id)
{
return _dt.Tables["Customer"].Rows.Find(customer_id);
}
The calling method would have to check for null beeing returned from the method, since an invalid customer_id would cause Find() tu return null.
Try using short type instead of Int32.
I would like to achieve same result as the below query using Hibernate SQL, i.e., I would like to get two random records from the table whose ID is not equal to 300. I am using Hibernate 4.1 and Oracle 11g. I ran the below query on Toad and it gives 2 random records. But, when I try to run the HQL, there is error to do with the usage of "DBMS_RANDOM.value".
SELECT * FROM
( SELECT *
FROM table
where ID != '300'
AND q_ID=125
ORDER BY DBMS_RANDOM.value
)WHERE rownum < 3
;
I tried creating criteria and query, but both give Hibernate errors:
Hibernate Message: Invalid path: 'DBMS_RANDOM.RANDOM' [from com.model.table tab where tab.ID != '33092' ORDER BY DBMS_RANDOM.RANDOM]
and my actual hibernate query is:
Query query = session.createQuery("from table tab where tab.ID != '" +agrmId+"' ORDER BY DBMS_RANDOM.RANDOM").setMaxResults(2);
I also tried ORDER BY rand() and that gives an Oracle error.
Thank you for any help.
I solved the problem by adding a property tag in the hibernate mapping file:
<property name="constVal" formula="DBMS_RANDOM.RANDOM" type="long"/>
and then, in the POJO class, I added a variable with getter and setter methods:
private long constVal;
then, in the DAO class, I added the following query:
Criteria crit1 = session.createCriteria(table.class);
crit1.add(Restrictions.ne("id",300));
crit1.add(Restrictions.eq("quesId",125));
crit1.addOrder(Order.asc("constVal"));
crit1.setMaxResults(2);
and that solved it.
Query:
select *
from easquestionsinfo
where questionname in(select questionname
from easresponseinfo
where isconflict = 'yes')
This query works fine and returns me the records from table 'easquestioninfo' when questionname is equal to the one returned by the inner query which returns set of questionname where isconflict='yes'.
JPA supports JPQL, SQL, and Criteria.
You can execute this SQL directly using createNativeQuery().
For JPQL, it depends on your object model, perhaps something like,
Select q fom QuestionInfo q where q.name in (Select r.name from ResponseInfo q2 where r.isConflict = 'yes')
See,
http://en.wikibooks.org/wiki/Java_Persistence/JPQL