Hibernate的HQl語句集錦

[size=large]Hibernate---HQL[/size]

[size=medium]1、多表左連接：[/size]

String hql = "select count(*) " +
                        " from SysMsgUserLink a " +
                        " left join a.sysMsg b  " +
                        " left join a.sysRevUser c  " +
                        " left join a.sysSendUser d " +
                        " where ... ";

[size=medium]2、左連接加子查詢：[/size]

String hql = "select count(*) " +
                        " from SysMsgUserLink a " +
                        " left join a.sysMsg b  " +
                        " left join a.sysRevUser c  " +
                        " left join a.sysSendUser d " +
                        " where ... " +
                        " and a.linkId in(" +
                        " select a.linkId " +
                        " from SysMsgUserLink a " +
                        " where ... ";

[size=medium]注意的關鍵點：
1、進行左連接的兩張表在建立Model層時，就必須註解清楚其關聯，否則會報 “無法識別該屬性”的錯誤
2、其實跟sql是一樣的用法，只是將數據庫中的表名直接換成對象名稱即可[/size]