Page 300 - TP_IT_V1.0_C10_flipbpookl
P. 300

Domain
                                                     Columns or Fields or Attributes                    5000,100000

                  Primary
                    Key           EMP_ID             NAME                POSTS              Salary
                                    E1         Rahul               Clerk                    30000

                 Rows               E2         Kapil               Manager                  90000
                Records                                                                                      Cardinality    (No. of Rows) = 4
                or Tuples           E3         Manoj               Clerk                    90000

                                    E4         Mukesh              Peon                     20000

                                                     Degree (No. of Columns) = 4                Data Value


              Basic Terminologies of RDBMS
              Some of the important terms of RDBMS are as follows:
              •  Entity: It is a real-world object about which information is to be stored in a database. For example, if we want to
                store information about an entity Student in a school, then we need to have his admission number, roll number,
                name, father’s name, date of birth, etc. These details associated with the entity are called attributes. Each entity
                is a collection of these attributes associated with it. So, roll number, name, admission number, etc., are attributes
                associated with the entity student. These attributes are represented in the form of columns.
              •  Tables: Tables are the basic structure of a database where data is stored. A table is a collection of logically related
                records. It is organised as a set of columns and can have any number of rows. Each row represents a record, while
                each column represents a field or attribute of that record.
              •  Data Values: Data values are the raw data represented in numeric, character or alphanumeric form.
              •  Fields/Columns: Fields or columns are the individual pieces of data stored within a table. Each field has a data type
                associated with it, such as text, number, date, etc. A field is the smallest entity in the database. A collection of fields
                makes a record, a collection of records makes a table, and a collection of tables make a database.
              •  Records/Rows: Records or rows are individual entries within a table. The data values for all the fields related to a
                person or object is called a record. Each row represents a single instance of data, with each column containing a
                specific attribute or value for that instance.
              •  Keys: A key is a field or combination of fields that uniquely identify a record (row) in a table. Keys are essential for data
                integrity and for establishing relationships between tables in a relational database management system (RDBMS).
              •  Relationships: Relationships define how tables within a database are related to each other. Common types of
                relationships include one-to-one, one-to-many, and many-to-many. These relationships are established using foreign
                keys, which are fields in one table that reference the primary key of another table.
              •  Constraints: Constraints are rules that enforce data integrity within a database. They define the conditions that
                must be met for data to be inserted, updated, or deleted in a table. Common types of constraints include primary
                key constraints, foreign key constraints, unique constraints, and check constraints.
              •  Queries: Queries are commands or statements used to retrieve, manipulate, or analyse data within a database.
                They allow users to perform tasks such as selecting specific records, calculating aggregate values, updating data,
                and joining multiple tables together.
              •  Degree: This refers to the number of attributes or columns in a table. For example, if a table has five columns
                (attributes), then the degree of the table is 5.
              •  Cardinality: This refers to the number of tuples or rows in a table. For example, if a table has 100 rows, then the
                cardinality of the table is 100.


                298   Trackpad Information Technology (Ver. 1.0)-X
   295   296   297   298   299   300   301   302   303   304   305