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pages/总复习2023t1.md

@@ -957,7 +957,7 @@
 					- DONE Review relational algebra https://www.geeksforgeeks.org/introduction-of-relational-algebra-in-dbms/
 					- LATER review lab2
 					- LATER SQL join
-			- LATER Block 2
+			- DONE Block 2
 				- DONE EER
 					- Most useful additional concept of EER model:
 					  specialization/generalization.
@@ -1005,7 +1005,10 @@
 							- The instances of a potential subclass participate in a relationship unique to that subclass.
 			- DONE Block 3
 				- DONE DB transaction management
-					- LATER anomalies
+					- NOW anomalies
+					  :LOGBOOK:
+					  CLOCK: [2023-06-14 Wed 16:41:52]
+					  :END:
 						- DONE Deadlock and how it can be resolved. #flashcard
 							- A deadlock is a situation in which two or more transactions are unable
 							  to proceed because each is waiting for a resource held by the other,
@@ -1073,31 +1076,24 @@
 						- Boyce-Codd Normal Form (BCNF): BCNF is a stricter form of 3NF that ensures that each determinant in a table is a candidate key. In other words, BCNF ensures that _each non-key attribute is dependent only on the candidate key._
 						- Fourth Normal Form (4NF): 4NF is a further refinement of BCNF that ensures that _a table does not contain any multi-valued dependencies._
 						- Fifth Normal Form (5NF): 5NF is the highest level of normalization and involves decomposing a table into smaller tables to _remove data redundancy and improve data integrity._
-			- DONE Block 4
+			- LATER Block 4
 				- DONE Distributed DBMS
-				  collapsed:: true
 					- DONE client server arch
-					  collapsed:: true
 						- Computers (client) connected over wired or wireless local area network (LAN)
 						- The database itself and the DBMS are stored on a central device called the database server, which is also connected to the network.
 					- Distributed Database
-					  collapsed:: true
 						- A logically interrelated collection of shared data (and a description of this data), physically spread over a computer network.
 					- Distributed DBMS
-					  collapsed:: true
 						- Software system that permits the management of the distributed database and makes the distribution transparent to users.
 					- the key issues
-					  collapsed:: true
 						- Fragmentation
 						- Allocation
 						- Replication
 					- importance and different types of fragmentation
-					  collapsed:: true
 						- Horizontal
 						- Vertical
 						- Mixed
 					- different types of transparency
-					  collapsed:: true
 						- Distribution Transparency: The database feels as a single, logical entity
 						- Transaction Transparency: Ensures that all distributed transactions maintain distributed database’s integrity and consistency.
 						- Performance Transparency: must perform as if it were a centralized DBMS.
@@ -1125,54 +1121,41 @@
 						- XSD: a more comprehensive method of defining content model of
 						  an XML document.
 				- DONE Data Mining
-				  collapsed:: true
 					- concept
-					  collapsed:: true
 						- The process of extracting valid, previously unknown, comprehensible,
 						  and actionable information from large databases and using it to make
 						  crucial business decisions.
 					- different applications
-					  collapsed:: true
 						- Retail / Marketing
 						- Banking
 						- Insurance
 						- Medicine
 					- basic techniques
-					  collapsed:: true
 						- predictive modelling,
-						  collapsed:: true
 							- uses observations to form a model of the important characteristics of some
 							  phenomenon
 						- database segmentation,
-						  collapsed:: true
 							- Uses unsupervised learning to discover homogeneous subpopulations in a database to improve the accuracy of the profiles.
 						- link analysis,
-						  collapsed:: true
 							- Establishing links, called associations, between the individual
 							  records, or sets of records, in a database.
 						- deviation detection.
-						  collapsed:: true
 							- Identifies outliers, which express deviation from some previously
 							  known expectation and norm.
 				- DONE NoSQL
-				  collapsed:: true
 					- the motivation for NoSQL
-					  collapsed:: true
 						- By giving up ACID constraints, one can achieve
 						  much higher performance and scalability.
 					- explain the concepts of NoSQL
-					  collapsed:: true
 						- NoSQL databases (aka "not only SQL") are non-tabular databases and store
 						  data differently than relational tables. NoSQL databases come in a
 						  variety of types based on their data model. The main types are document,
 						  key-value, wide-column, and graph. They provide flexible schemas and
 						  scale easily with large amounts of data and high user loads.
 					- explain the application areas of NoSQL
-					  collapsed:: true
 						- NoSQL is an alternative, non-traditional DB technology to be
 						  used in large scale environments where (ACID) transactions are not a priority.
 						- CAP theorem:
-						  collapsed:: true
 							- There are 3 main properties for distributed management:
 							  1.  Consistency → A data item has the same value at the same time (to
 							      ensure coherency).