"QuerySyntaxException: unexpected token: UNION ..." in Hibernate

Issue

• Encountering exception executing a UNION query using JPAQL / HQL

... org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: UNION near line 1, column 99 [SELECT ... from ... UNION ... SELECT ... from ... ]
        at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:74)
        at org.hibernate.hql.internal.ast.ErrorCounter.throwQueryException(ErrorCounter.java:91)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:287)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:186)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:141)
        at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115)
        at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:76)
        at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:150)
        at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:302)
        at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:240)
        at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1907)
        at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:291)