From 1cd25154c87d6deddc2915e1665e9d60fcde7f78 Mon Sep 17 00:00:00 2001 From: Ryan Date: Wed, 14 Jun 2023 16:55:26 +0800 Subject: [PATCH] Auto saved by Logseq --- pages/总复习2023t1.md | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/pages/总复习2023t1.md b/pages/总复习2023t1.md index 80c4067..7780b6d 100644 --- a/pages/总复习2023t1.md +++ b/pages/总复习2023t1.md @@ -1066,7 +1066,7 @@ transactions active at time of crash. - DONE Normalization background-color:: yellow - - DONE Functional dependencies [g4g](https://www.geeksforgeeks.org/types-of-functional-dependencies-in-dbms/) + - DONE Functional dependencies [g4g](https://www.geeksforgeeks.org/types-of-functional-dependencies-in-dbms/) #flashcard - In a relational database management, functional dependency is a concept that specifies the relationship between two sets of attributes where one attribute determines the value of another attribute. It is denoted as **X → Y**, where the attribute set on the left side of the arrow, **X** is called **Determinant** , and **Y** is called the **Dependent**. @@ -1075,29 +1075,29 @@ CLOCK: [2023-06-01 Thu 17:38:55]--[2023-06-01 Thu 17:38:56] => 00:00:01 :END: - DONE kinds of NF [tutorial](https://www.geeksforgeeks.org/normal-forms-in-dbms/) - - First Normal Form (1NF): This is the most basic level of + - First Normal Form (1NF): :-> This is the most basic level of normalization. In 1NF, each table cell should contain _only a single value, and each column should have a unique name_. The first normal form helps to eliminate duplicate data and simplify queries. - - Second Normal Form (2NF): 2NF eliminates redundant data by requiring that each _non-key attribute_ be dependent on the primary key. This means that _each column should be directly related to the primary key_, and not to other + - Second Normal Form (2NF): :-> 2NF eliminates redundant data by requiring that each _non-key attribute_ be dependent on the primary key. This means that _each column should be directly related to the primary key_, and not to other columns. - - Third Normal Form (3NF): 3NF builds on 2NF by requiring + - Third Normal Form (3NF): :-> 3NF builds on 2NF by requiring that _all non-key attributes are independent of each other._ This means that each column should be directly related to the primary key, and not to any other columns in the same table. - - 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._ + - 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._ - LATER Block 4 - DONE Distributed DBMS - - DONE client server arch + - DONE client server arch #flashcard - 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 + - Distributed Database #flashcard - A logically interrelated collection of shared data (and a description of this data), physically spread over a computer network. - - Distributed DBMS + - Distributed DBMS #flashcard - Software system that permits the management of the distributed database and makes the distribution transparent to users. - - the key issues + - the key issues #flashcard - Fragmentation - Allocation - Replication - - importance and different types of fragmentation + - importance and different types of fragmentation #flashcard - Horizontal - Vertical - Mixed