From 28b4eed00da370cca26a143e236b395695697f22 Mon Sep 17 00:00:00 2001 From: Ryan Date: Thu, 15 Jun 2023 09:27:27 +0800 Subject: [PATCH] Auto saved by Logseq --- ...op.md => 2023-06-15T01_27_27.434Z.Desktop.md} | 302 +++++++++++------- 1 file changed, 181 insertions(+), 121 deletions(-) rename logseq/bak/pages/总复习2023t1/{2023-06-14T07_11_54.910Z.Desktop.md => 2023-06-15T01_27_27.434Z.Desktop.md} (83%) diff --git a/logseq/bak/pages/总复习2023t1/2023-06-14T07_11_54.910Z.Desktop.md b/logseq/bak/pages/总复习2023t1/2023-06-15T01_27_27.434Z.Desktop.md similarity index 83% rename from logseq/bak/pages/总复习2023t1/2023-06-14T07_11_54.910Z.Desktop.md rename to logseq/bak/pages/总复习2023t1/2023-06-15T01_27_27.434Z.Desktop.md index cbe9471..900e690 100644 --- a/logseq/bak/pages/总复习2023t1/2023-06-14T07_11_54.910Z.Desktop.md +++ b/logseq/bak/pages/总复习2023t1/2023-06-15T01_27_27.434Z.Desktop.md @@ -870,49 +870,51 @@ :LOGBOOK: CLOCK: [2023-06-04 Sun 16:27:23]--[2023-06-04 Sun 16:54:55] => 00:27:32 :END: - - LATER Block 1 + - DONE Block 1 + deck:: 2023t1/database + collapsed:: true - DONE DBMS - Database is :-> a shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. - id:: 64895ec0-d724-4159-a95d-657afd171c29 + id:: 648974ba-3221-48b2-8f9c-2d9275174f48 - Table :-> A collection of related data organized into rows (also called records) and columns (also called fields). - id:: 64895ec0-2290-4f62-8711-45e99803c82e + id:: 648974ba-7b5a-4cff-8d21-3bcc7e0c1fe8 - Row/Record :-> A single set of data in a table, representing a specific instance or entity. - id:: 64895ec0-12a9-402d-8c1d-64c40e169bb2 + id:: 648974ba-d192-4027-945a-9c6113ac218f - Column/Field :-> A specific attribute or data element within a table. - id:: 64895ec0-2aed-4aa8-a34f-446fd7715db6 + id:: 648974ba-89e7-434a-b242-68a1ea3f7f6b - Primary Key :-> A unique identifier for each row/record in a table. It ensures the integrity and uniqueness of the data. - id:: 64895ec0-7339-477c-b765-b12fd18e9df4 + id:: 648974ba-611e-4d5c-849b-9cd57b7bddb9 - Foreign Key :-> A field in one table that refers to the primary key in another table, establishing a relationship between the two tables. - id:: 64895ec0-75e5-4378-aa9c-b4af6d7d37c9 + id:: 648974ba-bc0d-4b78-a8cb-7a081ca1b2ac - Relationship :-> The connection between tables based on common data values, such as primary and foreign keys. - id:: 64895ec0-ab80-4eed-bb91-0911b1954368 + id:: 648974ba-851d-42a7-95c1-2619fed22d3a - Normalization :-> The process of organizing and structuring a database design to eliminate redundancy and improve data integrity. - id:: 64895ec0-8b79-4172-8cad-25e4edada659 + id:: 648974ba-53b0-4176-b67b-cd51d1ea09c6 - Index :-> A data structure that improves the retrieval speed of data from a database table by creating a quick reference to the location of the data. - id:: 64895ec0-f3cd-4625-b2ca-6e94f870b34d + id:: 648974ba-2246-42c3-aa0c-7609107af7c5 - Query :-> A request for data or information from a database, usually written using Structured Query Language (SQL). - id:: 64895ec0-df79-46a4-8fb2-09b34a414c9c + id:: 648974ba-4b3e-4f99-90fd-b4c9a1a43a53 - SQL (Structured Query Language) :-> A programming language used to manage and manipulate relational databases. It allows you to create, modify, and retrieve data from databases. - id:: 64895ec0-4de4-4cfd-8042-7f92458a8a26 + id:: 648974ba-a844-4e21-a1ca-e0b26668f1b7 - CRUD Operations :-> An acronym for Create, Read, Update, and Delete operations, which are the basic operations used to manage data in a database. - id:: 64895ec0-77ed-4253-947e-2a54c4235a05 + id:: 648974ba-34d4-49df-91c9-b44b018120c6 - ACID (Atomicity, Consistency, Isolation, Durability) :-> A set of properties that guarantee the reliability and integrity of database transactions. - id:: 64895ec0-e18b-4340-8a24-98b2cbaec1fd + id:: 648974ba-4174-45b7-8903-38ffea39a200 - Data Integrity :-> The accuracy, consistency, and reliability of data stored in a database. - id:: 64895ec0-023b-47dc-96bd-7a4c52fd9717 + id:: 648974ba-7797-4a43-b644-f0780da5121b - Database Schema :-> The structure or blueprint of a database, defining the tables, fields, relationships, and constraints. - id:: 64895ec0-0c9b-49fc-923d-264841105690 + id:: 648974ba-7b5c-45d1-ac86-ef7211c9672a - Database Management System (DBMS) :-> Software that provides an interface to interact with databases, managing their creation, modification, and retrieval. - id:: 64895ec0-60c1-468f-bc13-bd65c736a682 + id:: 648974ba-627d-463c-9237-56777d45b8af - DONE basic concepts of Relational model - A data model :- > a graphical description of the components of database. - A relation, is :-> a two-dimensional table arranged in columns and rows. - id:: 64895ec0-a8ef-4e61-8e31-ce2b319a459b + id:: 648974ba-40ec-4600-af39-d438a5f75339 - A relational database is :-> a collection of relations. - id:: 64895ec0-4f99-4abd-a0f1-a0707ff20bd7 + id:: 648974ba-c76d-4f2b-a8ad-ef1ad3a16b2c - Candidate Key #flashcard - id:: 64895ec0-44d2-4816-9201-492149a1e26e + id:: 648974ba-a2f3-43a1-a5ea-c170c68314e1 - A set of attributes that uniquely identifies a tuple within a relation. - Uniqueness : In each tuple, candidate key uniquely identify @@ -920,45 +922,44 @@ - Irreducibility: No proper subset of the candidate key has the uniqueness property. - Primary Key #flashcard - id:: 64895ec0-057c-49f6-8fd9-0fc599e49e0a + id:: 648974ba-c5dc-44cb-8894-8f5838714f2a - Candidate key selected to identify tuples uniquely within relation. - Foreign Key #flashcard - id:: 64895ec0-2bf4-4bf5-92f3-b266cfcce167 + id:: 648974ba-da05-48b6-aded-75d1ea5f1342 - Attribute, or set of attributes, within one relation that matches candidate key of some (possibly same) relation. - Composite Key #flashcard - id:: 64895ec0-7b2e-4031-97ca-157c1864ac1c + id:: 648974ba-7242-4c00-b67b-5418c3f71e77 - A candidate key that consists of two or more attributes. - Recursive Relationship #flashcard - id:: 64895ec0-96f6-4a17-8d67-ddd8c7679066 + id:: 648974ba-eb07-4e80-a1c3-87555fb04d1a - Relationship type where same entity type participates more than once in different roles. - Multiplicity :-> number (or range) of possible - id:: 64895ec0-3514-4e82-acf6-f25238116bb7 + id:: 648974ba-5d96-4c64-a1b0-e9e61aa3563a occurrences of an entity type that may relate to a single occurrence of an associated entity type through a particular relationship. ![image.png](../assets/image_1686723218703_0.png) - Cardinality #flashcard - id:: 64895ec0-4ad7-43f2-80fc-489bc0a07ec1 + id:: 648974ba-b24d-40a3-8669-9dbc85dedaf7 - Describes {{c1 maximum}} number of possible relationship occurrences for an entity participating in a given relationship type. - id:: 64895ec0-e8d2-47e1-97b8-d81ed8d62f64 + id:: 648974ba-ea33-489d-bb7b-1951685babd0 - Participation #flashcard - id:: 64895ec0-c4c3-400e-9cb6-08f722328773 + id:: 648974ba-6dc5-4805-9dfd-7db5a83efe3f - Determines whether all or only some entity occurrences participate in a relationship. - Gives the minimum number for an entity occurrences participating in a given relationship type. - Ternary relationship #flashcard - id:: 64895ec0-0897-4857-b763-0349ae186d62 + id:: 648974ba-9b7a-4543-b243-e7a78cfc8175 - a ternary relationship is not the same as three binary relationships! - - LATER basic concepts associated with Entity-Relationship(ER) model. + - DONE basic concepts associated with Entity-Relationship(ER) model. - LATER Forming sql queries - collapsed:: true - DONE Review relational algebra https://www.geeksforgeeks.org/introduction-of-relational-algebra-in-dbms/ - LATER review lab2 - LATER SQL join - - LATER Block 2 - - LATER EER + - DONE Block 2 + - DONE EER - Most useful additional concept of EER model: specialization/generalization. - Specialization @@ -973,6 +974,7 @@ id:: 64896085-645b-408f-b17a-109b6cd82aeb specialization/generalization: - participation constraints :-> Determines whether every member in superclass + id:: 6489683b-319a-4173-a55b-6fa3b2c09aeb must participate as a member of a subclass. - May be mandatory or optional. #flashcard id:: 648960d0-ae7f-4452-a1b9-cab8a9b13443 @@ -980,14 +982,10 @@ member of subclass - Optional: member of superclass may be member of subclass. - - disjoint constraints :-> Describes relationship between members of the - subclasses and indicates whether member of a - superclass can be a member of one, or more than - one, subclass. #flashcard - - Disjoint: member of superclass is member of at - most one subclass - - Disjoint: member of superclass is member of at - most one subclass + - disjoint constraints :-> Describes relationship between members of the subclasses and indicates whether member of a superclass can be a member of one, or more than one, subclass. #flashcard + id:: 6489683b-039f-4161-94b1-91177f713ee5 + - Disjoint: member of superclass is member of at most one subclass (or) + - Nondisjoint: member of superclass can be member of more than one subclass (and) - Superclass / Subclass - Superclass :-> An entity type that includes one or more distinct id:: 64895f2f-b868-46ec-9d80-7079eaf3197d @@ -1002,43 +1000,82 @@ - Subclass :-> A distinct subgrouping of occurrences of an entity id:: 64895f39-d886-436b-9afe-ba75d37c8b45 type. - - When to use them? either one or both - 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 + - When to use them? either one or both #flashcard + id:: 6489683b-7d47-4246-afdf-83fdb35a00f6 + - There are attributes that apply to some (but not all) instances of an entity. + - The instances of a potential subclass participate in a relationship unique to that subclass. + - DONE Designing databases + - Understand Database Design Methodology #flashcard + - Conceptual database design + - The process of constructing a model of the data used in an enterprise, independent of all physical considerations. + - Logical database design + - Maps the conceptual data model on to a logical model (e.g. relational), but independent of a particular DBMS and other physical considerations. + - Physical database design + - The process of producing a description of the implementation of the database (tailored to specific DBMS); + - general steps for Database Design Methodology. #flashcard + - Gather requirements + - Conceptual database design + - Logical database design + - Physical database design + - LATER SQL + - purpose and importance of SQL. + - retrieve data from database and formulate queries using SELECT and + - Use compound WHERE conditions. + - Sort query results using ORDER BY. + - Use aggregate functions. + - Group data using GROUP BY and HAVING. + - Join tables together. + - Use subqueries. - DONE Block 3 collapsed:: true - DONE DB transaction management - - DONE ACID (Atomicity, Consistency, Isolation, Durability): A set of properties that guarantee the reliability and integrity of database transactions. - - Atomicity: The property that ensures a transaction is treated as a single, indivisible unit of work. It either executes all its operations successfully or rolls back to the initial state if any operation fails. - - Consistency: The property that ensures a transaction transforms the database from one consistent state to another consistent state. It maintains data integrity and adheres to defined business rules. - - Isolation: The property that ensures concurrent transactions do not interfere with each other. Each transaction operates in isolation until it completes, preventing interference or conflicts. - - Durability: The property that ensures committed changes made by a transaction are permanently saved and will survive any subsequent system failures or crashes. + - DONE Deadlock and how it can be resolved. #flashcard + id:: 64841da4-d8ce-46f5-bbe6-4dee620cde75 + - 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, + resulting in a circular dependency and a system halt. It is a form of + resource contention that can occur in concurrent systems, including + database management systems. + - Example: + - Cascading rollback #flashcard + id:: 64897f0b-dda6-4cc3-a9c3-cf630bcb0658 + - Cascading Rollback: a transaction (T1) causes a + failure and a rollback must be performed. Other + transactions dependent on T1's actions must also + be rollbacked, thus causing a cascading effect. + - One transaction's failure causes many to fail. + - DONE ACID (Atomicity, Consistency, Isolation, Durability): A set of properties that guarantee the reliability and integrity of database transactions. #flashcard + id:: 64841da4-0055-4d34-9f61-1402ff068ec7 + collapsed:: true + - Atomicity: :-> The property that ensures a transaction is treated as a single, indivisible unit of work. It either executes all its operations successfully or rolls back to the initial state if any operation fails. + id:: 64841d38-4ea9-4b76-8585-8b9de23915da + - Consistency: :-> The property that ensures a transaction transforms the database from one consistent state to another consistent state. It maintains data integrity and adheres to defined business rules. + id:: 64841d38-2854-4dfb-8f21-0013fca66a0a + - Isolation: :-> The property that ensures concurrent transactions do not interfere with each other. Each transaction operates in isolation until it completes, preventing interference or conflicts. + id:: 64841d38-fd2b-435e-bd45-3bf487a74b6f + - Durability: :-> The property that ensures committed changes made by a transaction are permanently saved and will survive any subsequent system failures or crashes. + id:: 64841d38-950c-431e-8f28-ece98e230554 - DONE Concurrency control - - DONE Meaning of serialisability. - - DONE How locking can ensure serialisability. + - DONE Meaning of serialisability. #flashcard + id:: 648428e1-5136-4d15-97c0-12087085b47f + - The objective of serialisability is to find nonserial schedules that are equivalent to some serial schedule. Such a schedule is called serialisable. + - DONE How locking can ensure serialisability. #flashcard + id:: 64841da4-8812-405f-b49a-69eec9a069d2 - Locking achieves serializability by using locks to control access to shared resources (e.g., database objects like tables or rows) and prevent conflicts between concurrent transactions. - - DONE 2PL + - DONE 2PL #flashcard + id:: 64841da4-eab4-40db-819f-249fe1437250 - In the 2PL protocol, transactions acquire and release locks on database objects (e.g., tables, rows) in two distinct phases: the growing phase and the shrinking phase. - - DONE Deadlock and how it can be resolved. - - 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, - resulting in a circular dependency and a system halt. It is a form of - resource contention that can occur in concurrent systems, including - database management systems. - - DONE How timestamping can ensure serialisability. + - DONE How timestamping can ensure serialisability. #flashcard + id:: 64842000-07a7-4439-8ce6-7789e0a3358d - By using transaction timestamps and enforcing the read and write validation checks, concurrency control mechanisms can ensure that transactions are executed in a way that maintains data consistency and serializability. - - DONE Recovery Control + - ==DONE Recovery Control== - DONE Some causes of database failure. - System crashes, resulting in loss of main memory. - Power failures @@ -1047,20 +1084,23 @@ - Natural physical disasters. - User mistakes. - Sabotage. - - DONE Purpose of transaction log file. + - DONE Purpose of transaction log file. #flashcard + id:: 64841f8f-5a9e-4f22-8f51-47931937998a - Contains information about all updates to database: - Transaction records. - Checkpoint records. - Often used for other purposes (for example, auditing). - For autiding - - DONE Purpose of checkpointing. + - DONE Purpose of checkpointing. #flashcard + id:: 64841f91-1d24-49f6-9f83-7c8b565c647f - When failure occurs, redo all transactions that committed since the checkpoint and undo all 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 + id:: 648428e1-e704-4e23-941d-af9833de6f93 - 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**. @@ -1069,122 +1109,142 @@ 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 + id:: 648974ba-7334-4e73-a0ae-6b8fc6ec99ab 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 + id:: 648974ba-cc9e-4cdf-a312-3af1bcab23f2 columns. - - 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._ + - Third Normal Form (3NF): :-> 3NF builds on 2NF by requiring + id:: 648974ba-f325-450e-aede-9a7d92bcf888 + 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**._ + id:: 64842000-c15a-4b8f-95c3-d6c6e49e4af0 - 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 + - Anomaly + - Update Anomalies #flashcard + - Insertion anomalies + - If there is a new row inserted in the table and it creates the + inconsistency in the table then it is called the insertion anomaly. For + example, if in the above table, we create a new row of a worker, and if + it is not allocated to any department then we cannot insert it in the + table so, it will create an insertion anomaly. + - Deletion anomalies + - If we delete some rows from the table and if any other information or + data which is required is also deleted from the database, this is called + the deletion anomaly in the database. For example, in the above table, + if we want to delete the department number ECT669 then the details of + Rajesh will also be deleted since Rajesh's details are dependent on the + row of ECT669. So, there will be deletion anomalies in the table. + - Modification anomalies + - When we update some rows in the table, and if it leads to the + inconsistency of the table then this anomaly occurs. This type of + anomaly is known as an updation anomaly. In the above table, if we want + to update the address of Ramesh then we will have to update all the rows + where Ramesh is present. If during the update we miss any single row, + then there will be two addresses of Ramesh, which will lead to + inconsistent and wrong databases. + - LATER Block 4 - DONE Distributed DBMS - collapsed:: true - - DONE client server arch - collapsed:: true + - DONE client server arch #flashcard + id:: 648974ba-9c11-4816-9d5e-0623dc4d4d45 - 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 + - Distributed Database #flashcard + id:: 648974ba-b13a-4f3f-8409-ea02b5ef5894 - A logically interrelated collection of shared data (and a description of this data), physically spread over a computer network. - - Distributed DBMS - collapsed:: true + - Distributed DBMS #flashcard + id:: 648974ba-997c-4f43-b2d6-d972cfc23d36 - Software system that permits the management of the distributed database and makes the distribution transparent to users. - - the key issues - collapsed:: true + - the key issues #flashcard + id:: 648974ba-4c63-4215-b420-d537c2a93675 - Fragmentation - Allocation - Replication - - importance and different types of fragmentation - collapsed:: true + - importance and different types of fragmentation #flashcard + id:: 648974ba-07aa-4c51-aa70-1c8dfb4570e7 - Horizontal - Vertical - Mixed - - different types of transparency - collapsed:: true + - different types of transparency #flashcard + id:: 648974ba-6db5-4d3a-af62-1695e7c3a9b7 - 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. - - advantages and disadvantages of distributed databases + - LATER advantages and disadvantages of distributed databases - DONE XML - collapsed:: true - - XML definition and basic concepts - collapsed:: true + - LATER XML definition and basic concepts #flashcard + id:: 648974ba-afab-457e-9633-488450e9e16f - eXtensible Markup Language - A meta-language (i.e. a language for describing other languages) that enables designers to create their own customised tags to provide functionality not available with HTML. - - Relational model versus XML - collapsed:: true + - LATER Relational model versus XML #flashcard + id:: 648974ba-d417-4eef-be28-46cd5894c5c7 - SQL - collapsed:: true - is a special-purpose programming language - You can: manage data in a relational databases. - XML - collapsed:: true - is a markup specification language - You can: design ways of describing information (text or data), usually for storage, transmission, or processing by a program (you can use it in combination with a programming language). - It says nothing about what you should do with the data (although your choice of element names may hint at what they are for). - - Well-formed XML, Valid XML - collapsed:: true + - LATER Well-formed XML, Valid XML #flashcard + id:: 648974ba-fb70-4207-8010-a8ddda35ccf7 - Adheres to basic structural requirements - Single root element - Matched tags, proper nesting - Unique attributes within elements - - DTD, XSD - collapsed:: true + - LATER DTD, XSD - DTD: Defines the valid syntax of an XML document - XSD: a more comprehensive method of defining content model of an XML document. + - LATER Practice reading and writing XML, XSD - DONE Data Mining - collapsed:: true - - concept - collapsed:: true + - concept #flashcard + id:: 648974ba-bf4c-4046-b7ce-510596ad421a - 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 + - different applications #flashcard + id:: 648974ba-7440-4ac2-8730-b33e9f50570c - Retail / Marketing - Banking - Insurance - Medicine - basic techniques - collapsed:: true - - predictive modelling, - collapsed:: true + - predictive modelling, #flashcard + id:: 648974ba-a007-420c-87db-1a029c1a39e6 - uses observations to form a model of the important characteristics of some phenomenon - - database segmentation, - collapsed:: true + - database segmentation, #flashcard + id:: 648974ba-18a0-474e-96de-6a824969d0ec - Uses unsupervised learning to discover homogeneous subpopulations in a database to improve the accuracy of the profiles. - - link analysis, - collapsed:: true + - link analysis, #flashcard + id:: 648974ba-0868-469f-9b8f-94a44163c87f - Establishing links, called associations, between the individual records, or sets of records, in a database. - - deviation detection. - collapsed:: true + - deviation detection. #flashcard + id:: 648974ba-a77e-47ba-9f0d-6ed14e880333 - Identifies outliers, which express deviation from some previously known expectation and norm. - DONE NoSQL - collapsed:: true - - the motivation for NoSQL - collapsed:: true + - the motivation for NoSQL #flashcard + id:: 648974ba-91af-424f-b392-928e947740de - By giving up ACID constraints, one can achieve much higher performance and scalability. - - explain the concepts of NoSQL - collapsed:: true + - explain the concepts of NoSQL #flashcard + id:: 648974ba-370b-44a8-9474-5b58d1d0dd28 - 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 + - explain the application areas of NoSQL #flashcard + id:: 648974ba-b39b-47b7-8b9f-ca9250bef8ba - 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 + - CAP theorem: #flashcard + id:: 648974ba-910d-42ae-89a9-5017194f6827 - There are 3 main properties for distributed management: 1. Consistency → A data item has the same value at the same time (to ensure coherency).