在Oracle SQL Developer中发现了未知的关系图符号 [英] Found an Unknown Relational Diagram Symbol in Oracle SQL Developer

问题描述

我正在使用Oracle SQL Developer(表建模部分)，并且发现了一个符号，似乎无法找到在线上任何地方的解释:

I am using Oracle SQL Developer (the table modeling part) and I have found a symbol that I can't seem to be able to find an explanation for anywhere online:

我已经搜索了一段时间，我全神贯注.我不确定到底是什么原因引起的，但我希望这里的某个人以前可能已经看过它并进行了解释.

I have been searching for a while now, and I'm at a total loss. I'm not sure what caused it in the first place, but I was hoping someone here might have seen it before and have an explanation.

推荐答案

您欺骗了我，否则我早就回答了.那不是"ER"符号. ER =实体关系.

You tricked me, or I would have answered this much sooner. That's not an 'ER' symbol. ER = Entity Relation.

该符号来自关系图，该关系图处理表和外键与实体和关系.

That symbol is from the relational diagram, which deals with tables and foreign keys vs entities and relations.

从文档中: 删除规则:当删除引用表中的行(在PK/UK索引中)并且包含该外键的表中存在具有该值的行时，将自动执行的操作:NO ACTION(在图中用交叉线显示) )对这些行不执行任何操作； CASCADE(用"X"显示)删除这些行； SET NULL(用小圆圈显示)将那些可以设置为null值的行中的所有列设置为null； RESTRICT(也由一条交叉线显示)可防止删除这些行.

From the docs: Delete Rule: Action to take automatically when a row in the referenced table (in PK/UK Index) is deleted and rows with that value exist in the table containing this foreign key: NO ACTION (shown by a crossing line in diagrams) performs no action on these rows; CASCADE (shown by an "X") deletes these rows; SET NULL (shown by a small circle) sets null all columns in those rows that can be set to a null value; RESTRICT (also shown by one crossing line) prevents those rows from being deleted.

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