HQL查询 蔚落 2022-06-12 05:07 202阅读 0赞 * 一HQL基本认识 * 二HQL查询 * 简单查询 * 实体对象查询 * 条件查询 * 分页查询 * 对象导航查询 * 连接查询 * 统计查询 * 三总结 # 一、HQL基本认识: # HQL(Hibernate Query Language)提供更加丰富灵活、更为强大的查询能力; HQL更接近SQL语句查询语法; \[select/delete/update…\]\[from…\]\[where…\]\[group by…\]\[having…\]\[order by…\] # 二、HQL查询: # ## 简单查询: ## (1)单一属性: ![这里写图片描述][SouthEast] (2)多个属性: ![这里写图片描述][SouthEast 1] ![这里写图片描述][SouthEast 2] ## 实体对象查询: ## (1)List方式: ![这里写图片描述][SouthEast 3] (2)迭代方式: ![这里写图片描述][SouthEast 4] 两者区别: list:默认情况下list每次都会发出sql语句,list会将数据放到缓存中,而不利用缓存 iterate:默认情况下iterate利用缓存,如果缓存中不存在会出现N+1问题 ## 条件查询: ## (1)like:返回list ![这里写图片描述][SouthEast 5] (2)占位符方法:返回query ![这里写图片描述][SouthEast 6] (3)方法链: ![这里写图片描述][SouthEast 7] (4)使用参数名方式: ![这里写图片描述][SouthEast 8] ![这里写图片描述][SouthEast 9] (5)获取日期的年和月:用date\_format ![这里写图片描述][SouthEast 10] ![这里写图片描述][SouthEast 11] ![这里写图片描述][SouthEast 12] (6)两个日期间数据的查询: ![这里写图片描述][SouthEast 13] ## 分页查询: ## ![这里写图片描述][SouthEast 14] setFirstResult(),从0开始; setMaxResults(),每页显示的记录数 ## 对象导航查询: ## ![这里写图片描述][SouthEast 15] ## 连接查询: ## 连接查询分为内连接和外连接(左连接和右连接) 1.内连接: ![这里写图片描述][SouthEast 16] 2.左连接: ![这里写图片描述][SouthEast 17] 3.右连接: ![这里写图片描述][SouthEast 18] ## 统计查询: ## ![这里写图片描述][SouthEast 19] 查询班级名称和学生人数:string hql = ![这里写图片描述][SouthEast 20] # 三、总结: # Hql是hibernate的核心查询,和sql差不多,目前学会了sql,linq,hql三种查询语言,现在学起来很轻松,多和以前学过的知识联系吧。 [SouthEast]: /images/20220612/3551c9cccb0e4f9c9d343797c06d84e0.png [SouthEast 1]: /images/20220612/d4ae3cf815a047be831d613fb0af7d87.png [SouthEast 2]: /images/20220612/e1ef7a3702ef441493f1908b44ee1b27.png [SouthEast 3]: /images/20220612/7bd4569bb9e24da5ae20cebdbfb9c235.png [SouthEast 4]: /images/20220612/f528055fcba44e82b96fab7c75dcb4eb.png [SouthEast 5]: /images/20220612/bbf25263e1ec4836912e057dc5c6dd41.png [SouthEast 6]: /images/20220612/cec959679dec4acea6f090e9ae2838bb.png [SouthEast 7]: /images/20220612/45279eaf7ba9475eb58bf0c7b7493558.png [SouthEast 8]: /images/20220612/078da64ba0104884b35fa573b419d41b.png [SouthEast 9]: /images/20220612/76b8f6a78d394256a1c3bdd30089bfa0.png [SouthEast 10]: /images/20220612/68817349282b4ec4994b8ce5af1944d3.png [SouthEast 11]: /images/20220612/6c18780dcded40118cd43862c10d04cf.png [SouthEast 12]: /images/20220612/6e801e396aba4f308d97dd010b0e7062.png [SouthEast 13]: /images/20220612/1793a8ccc7134c6cb55d0c6b8528ff9f.png [SouthEast 14]: /images/20220612/87f068f8bdb44ad7a1e2109288fabcc6.png [SouthEast 15]: /images/20220612/dcaf0b62e71346b091caff591676a6e7.png [SouthEast 16]: /images/20220612/6e8bfd8764bd4c77932867018734e9cb.png [SouthEast 17]: /images/20220612/f77abb543525434f95d334424488bc49.png [SouthEast 18]: /images/20220612/f468702bb75f4f2092ac7d2a9854600f.png [SouthEast 19]: /images/20220612/cd0779ab5fda4d038c215d0990355785.png [SouthEast 20]: /images/20220612/74dc3fa86548412aadde85257e942707.png
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