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logseq/bak/pages/总复习2023t1/2023-06-14T08_05_14.243Z.Desktop.md
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@ -582,7 +582,6 @@
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M. A Khan Secretary
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```
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- DONE memo report
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- Format
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- Abstract
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@ -874,46 +873,46 @@
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- LATER Block 1
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- DONE DBMS
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- Database is :-> a shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
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id:: 64895ec0-d724-4159-a95d-657afd171c29
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id:: 648974ba-3221-48b2-8f9c-2d9275174f48
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- Table :-> A collection of related data organized into rows (also called records) and columns (also called fields).
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id:: 64895ec0-2290-4f62-8711-45e99803c82e
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id:: 648974ba-7b5a-4cff-8d21-3bcc7e0c1fe8
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- Row/Record :-> A single set of data in a table, representing a specific instance or entity.
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id:: 64895ec0-12a9-402d-8c1d-64c40e169bb2
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id:: 648974ba-d192-4027-945a-9c6113ac218f
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- Column/Field :-> A specific attribute or data element within a table.
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id:: 64895ec0-2aed-4aa8-a34f-446fd7715db6
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id:: 648974ba-89e7-434a-b242-68a1ea3f7f6b
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- Primary Key :-> A unique identifier for each row/record in a table. It ensures the integrity and uniqueness of the data.
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id:: 64895ec0-7339-477c-b765-b12fd18e9df4
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id:: 648974ba-611e-4d5c-849b-9cd57b7bddb9
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- Foreign Key :-> A field in one table that refers to the primary key in another table, establishing a relationship between the two tables.
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id:: 64895ec0-75e5-4378-aa9c-b4af6d7d37c9
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id:: 648974ba-bc0d-4b78-a8cb-7a081ca1b2ac
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- Relationship :-> The connection between tables based on common data values, such as primary and foreign keys.
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id:: 64895ec0-ab80-4eed-bb91-0911b1954368
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id:: 648974ba-851d-42a7-95c1-2619fed22d3a
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- Normalization :-> The process of organizing and structuring a database design to eliminate redundancy and improve data integrity.
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id:: 64895ec0-8b79-4172-8cad-25e4edada659
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id:: 648974ba-53b0-4176-b67b-cd51d1ea09c6
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- 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.
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id:: 64895ec0-f3cd-4625-b2ca-6e94f870b34d
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id:: 648974ba-2246-42c3-aa0c-7609107af7c5
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- Query :-> A request for data or information from a database, usually written using Structured Query Language (SQL).
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id:: 64895ec0-df79-46a4-8fb2-09b34a414c9c
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id:: 648974ba-4b3e-4f99-90fd-b4c9a1a43a53
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- 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.
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id:: 64895ec0-4de4-4cfd-8042-7f92458a8a26
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id:: 648974ba-a844-4e21-a1ca-e0b26668f1b7
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- CRUD Operations :-> An acronym for Create, Read, Update, and Delete operations, which are the basic operations used to manage data in a database.
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id:: 64895ec0-77ed-4253-947e-2a54c4235a05
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id:: 648974ba-34d4-49df-91c9-b44b018120c6
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- ACID (Atomicity, Consistency, Isolation, Durability) :-> A set of properties that guarantee the reliability and integrity of database transactions.
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id:: 64895ec0-e18b-4340-8a24-98b2cbaec1fd
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id:: 648974ba-4174-45b7-8903-38ffea39a200
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- Data Integrity :-> The accuracy, consistency, and reliability of data stored in a database.
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id:: 64895ec0-023b-47dc-96bd-7a4c52fd9717
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id:: 648974ba-7797-4a43-b644-f0780da5121b
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- Database Schema :-> The structure or blueprint of a database, defining the tables, fields, relationships, and constraints.
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id:: 64895ec0-0c9b-49fc-923d-264841105690
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id:: 648974ba-7b5c-45d1-ac86-ef7211c9672a
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- Database Management System (DBMS) :-> Software that provides an interface to interact with databases, managing their creation, modification, and retrieval.
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id:: 64895ec0-60c1-468f-bc13-bd65c736a682
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id:: 648974ba-627d-463c-9237-56777d45b8af
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- DONE basic concepts of Relational model
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- A data model :- > a graphical description of the
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components of database.
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- A relation, is :-> a two-dimensional table arranged in columns and rows.
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id:: 64895ec0-a8ef-4e61-8e31-ce2b319a459b
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id:: 648974ba-40ec-4600-af39-d438a5f75339
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- A relational database is :-> a collection of relations.
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id:: 64895ec0-4f99-4abd-a0f1-a0707ff20bd7
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id:: 648974ba-c76d-4f2b-a8ad-ef1ad3a16b2c
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- Candidate Key #flashcard
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id:: 64895ec0-44d2-4816-9201-492149a1e26e
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id:: 648974ba-a2f3-43a1-a5ea-c170c68314e1
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- A set of attributes that uniquely identifies a tuple within a
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relation.
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- Uniqueness : In each tuple, candidate key uniquely identify
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@ -921,36 +920,36 @@
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- Irreducibility: No proper subset of the candidate key has the
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uniqueness property.
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- Primary Key #flashcard
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id:: 64895ec0-057c-49f6-8fd9-0fc599e49e0a
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id:: 648974ba-c5dc-44cb-8894-8f5838714f2a
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- Candidate key selected to identify tuples uniquely within
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relation.
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- Foreign Key #flashcard
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id:: 64895ec0-2bf4-4bf5-92f3-b266cfcce167
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id:: 648974ba-da05-48b6-aded-75d1ea5f1342
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- Attribute, or set of attributes, within one relation that
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matches candidate key of some (possibly same) relation.
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- Composite Key #flashcard
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id:: 64895ec0-7b2e-4031-97ca-157c1864ac1c
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id:: 648974ba-7242-4c00-b67b-5418c3f71e77
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- A candidate key that consists of two or more attributes.
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- Recursive Relationship #flashcard
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id:: 64895ec0-96f6-4a17-8d67-ddd8c7679066
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id:: 648974ba-eb07-4e80-a1c3-87555fb04d1a
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- Relationship type where same entity type participates
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more than once in different roles.
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- Multiplicity :-> number (or range) of possible
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id:: 64895ec0-3514-4e82-acf6-f25238116bb7
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id:: 648974ba-5d96-4c64-a1b0-e9e61aa3563a
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occurrences of an entity type that may relate to a
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single occurrence of an associated entity type
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through a particular relationship.
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- Cardinality #flashcard
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id:: 64895ec0-4ad7-43f2-80fc-489bc0a07ec1
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id:: 648974ba-b24d-40a3-8669-9dbc85dedaf7
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- Describes {{c1 maximum}} number of possible relationship occurrences for an entity participating in a given relationship type.
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id:: 64895ec0-e8d2-47e1-97b8-d81ed8d62f64
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id:: 648974ba-ea33-489d-bb7b-1951685babd0
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- Participation #flashcard
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id:: 64895ec0-c4c3-400e-9cb6-08f722328773
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id:: 648974ba-6dc5-4805-9dfd-7db5a83efe3f
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- Determines whether all or only some entity occurrences participate in a relationship.
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- Gives the minimum number for an entity occurrences participating in a given relationship type.
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- Ternary relationship #flashcard
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id:: 64895ec0-0897-4857-b763-0349ae186d62
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id:: 648974ba-9b7a-4543-b243-e7a78cfc8175
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- a ternary relationship is not the same as three binary relationships!
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- LATER basic concepts associated with Entity-Relationship(ER) model.
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- LATER Forming sql queries
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@ -1215,4 +1214,4 @@
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SCHEDULED: <2023-06-19 Mon>
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- {{embed ((647bf024-41f1-45e7-afaf-f49026e826d6))}}
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- 
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-
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-
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