sql - HQL Join - Path expected for join! hibernate -


i new hibernate , met following problem: got "path expected join!" exception when tried run query:

string hql = "select avg(t.price) ticket t join flight f f.number = '" + flightnumber + "'"; query query = this.session.createquery(hql);         list<double> list = query.list();

i wanted select average price of tickets have been sold given flight.

i have checked these links, did not solve problem: hql left join: path expected join hql inner join path expected join! error

my code is:

flight.hbm.xml

<?xml version="1.0"?><!doctype hibernate-mapping public  "-//hibernate/hibernate mapping dtd 3.0//en"  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping>     <class name="pck.flight" table="flight" catalog="airbook">         <id name="id" type="java.lang.integer">             <column name="id" />             <generator class="identity" />         </id>         <many-to-one name="sourceairport" class="pck.sourceairport" fetch="select">             <column name="sourceairportid" />         </many-to-one>         <many-to-one name="destinationairport" class="pck.destinationairport" fetch="select">             <column name="destinationairportid" />         </many-to-one>         <property name="number" type="string">             <column name="number" length="30" />         </property>         <property name="date" type="timestamp">             <column name="date" length="19" />         </property>         <property name="miles" type="java.lang.integer">             <column name="miles" />         </property>         <property name="numberofseats" type="java.lang.integer">             <column name="numberofseats" />         </property>         <property name="airplane" type="string">             <column name="airplane" length="30" />         </property>         <set name="tickets" table="ticket" inverse="true" lazy="true" fetch="select">             <key>                 <column name="flightid" />             </key>             <one-to-many class="pck.ticket" />         </set>     </class> </hibernate-mapping>

ticket.hbm.xml

<?xml version="1.0"?> <!doctype hibernate-mapping public "-//hibernate/hibernate mapping dtd 3.0//en"  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping>     <class name="pck.ticket" table="ticket" catalog="airbook">         <id name="id" type="java.lang.integer">             <column name="id" />             <generator class="identity" />         </id>         <many-to-one name="flight" class="pck.flight" fetch="select">             <column name="flightid" />         </many-to-one>         <many-to-one name="passenger" class="pck.passenger" fetch="select">             <column name="passengerid" />         </many-to-one>         <property name="price" type="java.lang.double">             <column name="price" precision="22" scale="0" />         </property>     </class> </hibernate-mapping>

all other queries without join work fine. not know problem is.

the correct query is:

select avg(t.price) ticket t join t.flight f f.number = :flightnumber

and altogether query execution:

transaction tx = session.begintransaction();  string hql = "select avg(t.price) ticket t join t.flight f f.number = :flightnumber"; query query = this.session.createquery(hql).setstring("flightnumber", flightnumber);  list<double> list = query.list();   tx.commit();

as explained in question linked to, , in hibernate documentation, joins use associations between entities. correct query is

select avg(t.price) ticket t join t.flight f f.number = :flightnumber

also note using parameters better solution concatenating values directly in query. handles quoting , escaping automatically, , doesn't have risk of hql injection.


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