what is RDBMS
RDBMS, or Relational Database Management System, refers to a type of database management system that organizes data into tables based on the relational model developed by E.F. Codd. Popular examples of RDBMS include SQL, MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. These systems are called relational because they structure data in a way that allows for the easy creation and management of relationships between different data tables.
Brief History of RDBMS:
Between 1970 and 1972, E.F. Codd introduced the concept of the relational database model through his influential papers. The RDBMS is fundamentally based on Codd's relational model, which revolutionized database management.
what is table/Relation?
properties of Relation
Each relation in a database is identified by a unique name. Relations do not include duplicate tuples, and the order of tuples within a relation is not fixed. All attributes in a relation are atomic, meaning each cell contains a single, indivisible value. A table is the most basic form of data representation in an RDBMS.
Let see Example of student Table
what is row or record?
A row in a table, also known as a record or tuple, represents a single entry and contains specific information related to that entry. It is a horizontal component of the table. For instance, a table with 5 records would have 5 distinct rows.
Key properties of a row include:
1. Each row is unique and no two rows can have identical values across all their columns.
2. All rows in the table adhere to the same format and have the same number of columns.
3. The order of the rows does not matter; rows are identified by their content rather than their position in the table.
what is column or Attribute?
A column, also known as an attribute, is a vertical component of a table that holds data related to a specific field. For example, a column labeled "name" would store all the information pertaining to students' names in the table.
Key properties of an attribute include:
1. Every attribute must have a distinct name.
2. Attributes can contain null values if no data is available.
3. Default values can be set for an attribute, which will be used if no other value is provided.
4. Attributes that uniquely identify each row in the table are known as the primary key.
what is Data item/cell:
A data item, also known as a cell, represents the smallest unit of data within a table. It is located at the intersection of a row (tuple) and a column (attribute).
Key properties of data items include:
1. Data items are atomic, meaning they contain a single, indivisible value.
2. All data items within a given column should come from the same domain or type of data.
3. For example, in a student table, data items might include values like "Ajeet," "24," and "BTech," each representing specific details in different cells of the table.
cardinality:
Cardinality refers to the total number of tuples (rows) present in a relation (table) at any given time. A table with a cardinality of 0 is referred to as an empty table.
For example, if the student table contains 4 rows, its cardinality is 4.
Domain:
The domain defines the set of permissible values for each attribute in a table. This can be specified using standard data types such as integers or floating-point numbers. For instance, an attribute named "Marital_Status" might be restricted to values like "married" or "unmarried."
NULL Values:
A NULL value in a table indicates that a field was left blank during record creation. This is distinct from fields filled with zero or containing spaces.
Data Integrity:
Data integrity encompasses several categories within a relational database management system (RDBMS):
1. Entity Integrity: Ensures that each row in a table is unique, preventing duplicate rows.
2. Domain Integrity: Enforces valid entries for a column by specifying constraints on the type, format, or range of values.
3. Referential Integrity: Maintains consistency by ensuring that rows cannot be deleted if they are referenced by other records.
4. User-Defined Integrity:Implements specific business rules defined by users, which are distinct from entity, domain, or referential integrity rules.
