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Operator in SQL?
Download PDF Google Drive Overview : What is an Operator in SQL? 1. Arithmetic operator Binary Operators Unary Operators 2. Comparison operators 3. Logical operators 4. Operators used to negate conditions
Functional Dependency ( DBMS )
Functional Dependency : The functional dependency is a relationship that exists between two attributes. It typically exists between the primary key and non-key attribute within a table. X → Y The left side of FD is known as a determinant , the right side of the production is known as a dependent . Types of Functional dependency : · Trivial functional dependency · Non-trivial functional dependency Trivial functional dependency : · It is what one attribute determine to another Attribute. In a DBMS System. E_No E_Name Salary E_City 101 XYZ 10,000 Landon 102 PQR 20,000 Tokyo 103 ABC 30,000 Tokyo If We Know the “ E_NO ” We can Obtain “ E_Name ”, “ E-City ” and “ Sal...
Data Abstraction
Short Note: Data Abstraction Data abstraction: It can be define as follows. 1. When the DBMS hides certain details of how data is stored and maintained, it provides What is called as the abstract view of data? 2. This is to simplify user-interaction with the system. 3. Complexity (of data and data structure) is hidden from users through several levels of Abstraction. Data abstraction is used for following purposes: 1. To provide abstract view of data. 2. To hide complicate data from user. 3. To simplify user interaction with DBMS.
Database Model ( DBMS )
Database Models · A data model is a collection of logical constructs used to represent data structure and relationship within the database. · A database model is used to represent the data into the database. · Database models are given as below: (1) Hierarchical Model · It organizes data in an upside-down tree structure. · There is a hierarchy of parent and child data segments. · It uses Parent Child Relationships. · Here root node is called parent node and root segment is called child node. · The parent can have none, one or more child nodes but child nodes can not have the multiple parent node. · That’s why it represents data into one-to-many relationship between two entities. Advantages : (1) Provide data sharing, data security and data integrity. (2) Parent/child relationship provides data simplicity. (3) Provide efficient 1-M relationship. Dis...