查询多个表放在一个集合中用union做连接

SELECT blood,BG,create_date,OGTT,flag FROM ((SELECT "空腹血糖" AS blood,t.`BG`,t.create_date,t.`OGTT`,t.`BGFLAG` AS flag FROM xuetang AS t WHERE t.PERSON_ID=1101020142011000001 AND t.`BG` IS NOT NULL )UNION ALL(SELECT "空腹血糖" AS blood, h.`BG`,h.`CREATE_DATE`,NULL,NULL AS flag FROM health_sugar AS h WHERE  h.PERSON_ID=1101020142011000001 AND h.`BG` IS NOT NULL )UNION ALL(SELECT "空腹血糖" AS blood,c.`SC_FBG`,c.CREATE_DATE,NULL,NULL AS flag FROM common_manager AS cWHERE c.PERSON_ID=1101020142011000001 AND c.`SC_FBG` IS NOT NULL )) AS cc ORDER BY cc.create_date DESC;

用union做连接时应该注意列必须一样多，如果一个表中有一列，另一个表没有则可以用null代替

 

HQL不支持union，用sql实现，Query query = session.createSQLQuery();