分类：映射关系

2021
01-29

聊聊PostgreSql table和磁盘文件的映射关系

在postgresql中Droptable会不会释放磁盘空间，今日以实操来见证--2019-01-1109:49:21droptable会不会释放空间createtabletab_todrop(idint,cnamevarchar(50),remarktext);insertintotab_todropselectgenerate_series(1,10000000),'wxgoodboy',md5('wxgoodboy');insertintotab_todropselectgenerate_series(1,10000000),'wxgoodboy',md5('wxgoodboy');--查看表大小qmstst=#selectpg_size_pretty(pg... 继续阅读 >

2020
10-30

Hibernate双向一对一映射关系配置代码实例

1、外键映射1.1、实体类packagecom.yl.bean;importjava.io.Serializable;/***公民实体类*/publicclassPersonimplementsSerializable{privateIntegerid;privateStringname;privatePersonCardcard;publicPerson(){}publicPerson(Integerid,Stringname,PersonCardcard){this.id=id;this.name=name;this.card=card;}publicIntegergetId(){returnid;}publicvo... 继续阅读 >

2020
10-30

Hibernate双向多对多映射关系配置代码实例

1、实体类packagecom.yl.bean;importjava.io.Serializable;importjava.util.Set;/***商品实体类*/publicclassGoodsimplementsSerializable{privateIntegerid;//商品idprivateStringgoodsName;//商品名privateDoubleprice;//商品价格privateStringremark;//备注privateSet<GoodsOrder>orderSet;//商品所属订单publicGoods(){}publicIntegergetId(){returnid;}publicvoidsetId... 继续阅读 >