How do I get the NextVal from an oracle Sequence thru NHibernate
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08-10-2019 - |
Question
I am working on c# .net 4.0 and using NHibernate to talk with an Oracle DB. You would think something as simple as this is already addressed somewhere but sadly its not. I need the NextVal from an Oracle sequence. I do not need to insert it a database as part of an Id or Primary key. I just need to use the next val on the c# side.
Can somebody help me out with xml mapping and C# file(or a link) to achieve this.
Thanks.
Something like
int NextValueOfSequence = GetNextValueofSequence();
public int GetNextValueOfSequence()
{
// Access NHibernate to return the next value of the sequence.
}
Solution
Mapping:
<sql-query name="GetSequence" read-only="true">
<return-scalar type="Int64"/>
<![CDATA[
SELECT SeqName.NEXTVAL from DUAL;
]]>
</sql-query>
Code:
Int64 nextValue = session.GetNamedQuery("GetSequence").UniqueResult<System.Int64>();
OTHER TIPS
This also does the trick.
<your session variable>.CreateSQLQuery("select <your sequence>.NEXTVAL from dual").UniqueResult<Int64>();
With NH4 I use this DB agnostic ISession extension method (obviously DB must support sequences)
public static T GetSequenceNextValue<T>(this ISession session, string sequenceName) where T : struct
{
var dialect = session.GetSessionImplementation().Factory.Dialect;
var sqlQuery = dialect.GetSequenceNextValString(sequenceName);
return session.CreateSQLQuery(sqlQuery).UniqueResult<T>();
}
There is a small correction in the mapping given by @Petr Kozelek
<sql-query name="GetSequence" read-only="true">
<return-scalar column="NextNo" type="Int64"/>
<![CDATA[
SELECT SeqName.NEXTVAL as NextNo from DUAL
]]>
</sql-query>
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