Auto saved by Logseq

2023-06-14 15:11:30 +08:00 · 2023-06-14 15:11:30 +08:00 · 3f993adc01
parent bdcd9786d9
commit 3f993adc01
1 changed files with 6 additions and 0 deletions
--- a/pages/总复习2023t1.md
+++ b/pages/总复习2023t1.md
@ -1002,6 +1002,12 @@
 						- Subclass :-> A distinct subgrouping of occurrences of an entity
 						  id:: 64895f39-d886-436b-9afe-ba75d37c8b45
 						  type.
+						- When to use them? eith
+						  1. There are attributes that apply to some (but
+						  not all) instances of an entity.
+						  2. The instances of a potential subclass
+						  participate in a relationship unique to that
+						  subclass.
 				- LATER designing ER diagram
 			- DONE Block 3
 			  collapsed:: true