diff --git a/pages/总复习2023t1.md b/pages/总复习2023t1.md
index a6116dd..00cac5c 100644
--- a/pages/总复习2023t1.md
+++ b/pages/总复习2023t1.md
@@ -1020,6 +1020,7 @@
 					- LATER SQL
 						- purpose and importance of SQL.
 							- SQL is a transform-oriented language with 2
+							  collapsed:: true
 							  major components: #flashcard
 								- A DDL for defining database structure.
 									- Create table
@@ -1029,6 +1030,11 @@
 									- Delete
 									- update
 									- Select
+							- Importance:
+								- it is non-procedural - you specify what
+								  information you require, rather than how to get it;
+								- it is essentially free-format.
+								- easy to learn
 						- retrieve data from database and formulate queries using SELECT and
 							- Use compound WHERE conditions.
 							- Sort query results using ORDER BY.