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jointly under trial for same offence.(1) When more persons than one are being tried jointly for the same offence, and a confession made by one of those persons affecting himself and some other of those persons is proved, the court may take into consideration the confession as against the other person as well as against the person who makes the confessionExplanation – "offence" as used in this section includes the abetment of or attempt to commit the offence.IllustrationsA and B are jointly tried
1. Trivial vs. Non-Trivial Dependency
These types describe the basic mathematical relationship between the sets of attributes.
* Trivial Functional Dependency: Occurs when the dependent (RHS) is a subset of the determinant (LHS). It is "trivial" because it doesn't provide new information.
* Logic: X \to Y is trivial if Y \subseteq X.
* Example: \{Student\_ID, Name\} \to \{Name\}.
* Non-Trivial Functional Dependency: Occurs when the dependent is not a subset of the determinant.
* Logic:
6. Constraints and Implementation
Constraints are rules applied to columns to ensure Data Integrity. They are usually defined during the CREATE TABLE process.
| Constraint | SQL Implementation Example | Purpose |
|---|---|---|
| NOT NULL | name VARCHAR(50) NOT NULL | Ensures a column cannot have an empty value. |
| UNIQUE | email VARCHAR(50) UNIQUE | Ensures all values in a column are different. |
| PRIMARY KEY | id INT PRIMARY KEY | Uniquely identifies each row (implies NOT NULL + UNIQUE). |
| FOREIGN
When designing an ER (Entity-Relationship) Diagram, there are two primary sets of symbolic notations: Chen's Notation (traditional/academic) and Crow's Foot Notation (modern/industry standard).
1. Chen’s Notation (Conceptual Focus)
Peter Chen’s original 1976 notation is highly detailed and uses distinct geometric shapes for every component. It is the gold standard for learning the theoretical foundations of databases.
Core Symbols
* Rectangle: Represents a Strong Entity (e.g., STUDENT).
* Double
Data models serve as the blueprint for how data is structured, stored, and manipulated. The evolution of these models reflects the growing need for flexibility and the ability to handle complex relationships.
1. Hierarchical Data Model
The Hierarchical Model is the oldest of the three, popularized by IBM's Information Management System (IMS) in the 1960s. It organizes data in a top-down, tree-like structure.
* Structure: Data is represented as a collection of "segments" connected by parent-child
Building on the 3-level architecture we discussed, Data Independence is the practical benefit of that structure. It is the ability to modify a database schema at one level without requiring a change to the schema at the next higher level.
This ensures that as your database grows or your hardware changes, you don't have to rewrite your entire software application.
1. Physical Data Independence
Physical data independence is the ability to change the Internal/Physical schema without affecting the Conceptual
1. Database Interfaces
A DBMS provides various interfaces to suit different types of users (from non-technical clerks to expert administrators).
* Menu-Based Interfaces: Primarily used for web clients and browsing. Users are presented with a list of options (menus) and do not need to know any query language.
* Forms-Based Interfaces: Common for "Naive Users." Users interact by filling out fields in a form (e.g., a bank account registration form). The DBMS then handles the insertion or retrieval.
Database approach chatercterstics
1. Self-Describing Nature of a Database System
Unlike a file system, where the structure of data is hardcoded into the application programs, a database system contains both the data and its complete definition.
* Metadata: The description of the database structure, data types, and constraints is stored in the DBMS Catalog (or Data Dictionary).
* Significance: This allows the DBMS software to work with different databases without knowing their specific structure