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Technical articles with clear explanations and examples
Binary Relationship in Database
A Binary Relationship is a relationship between two different entities in a database. It maps the role group of one entity with the role group of another entity, establishing how data in one table relates to data in another table. There are three types of cardinalities for binary relationships − One-to-One (1:1), One-to-Many (1:N), and Many-to-Many (M:N). One-to-One (1:1) In a one-to-one relationship, one instance of the first entity is mapped with only one instance of the second entity. The primary key of one entity is available as a foreign key in the other entity. This type of relationship is ...
Read MoreTernary Relationship in Database
In a Ternary Relationship, three different entities participate in a single relationship simultaneously. The relationship degree is 3. When determining cardinality, we consider it in the context of two entities relative to the third. Example: Mobile Manufacturing Company Consider a mobile manufacturing company with three entities − Mobile − The mobile models manufactured by the company. Part − Mobile parts which the company gets from suppliers. Supplier − Suppliers who supply mobile parts to the company. All three entities participate simultaneously in a SUPPLIES relationship ...
Read MoreOne-to-One Unary Relationship in DBMS
A One-to-One Unary Relationship (also called a recursive relationship) is an association within the same entity where one instance is related to exactly one other instance of the same entity type. This type of relationship creates a loop back to the same entity, allowing instances to be connected to other instances of their own type. Understanding One-to-One Unary Relationships In a one-to-one unary relationship, we have a single entity that participates in a relationship with itself. The key characteristic is that each instance can be related to at most one other instance of the same entity, and vice ...
Read MoreRDBMS terminologies
RDBMS (Relational Database Management System) uses specific terminologies to describe its components. These include Database, Table, Column, Row, and various types of keys. Let us see them one by one − Database A database is a collection of related tables. For example, a university database may contain tables like Student, Professors, Courses, etc. Table A table (also called a relation) is a collection of rows and columns that stores data about a specific entity. Here's an example of a Student table − ...
Read MoreReverse a Number in PL/SQL
PL/SQL is a block-structured language that combines SQL's functionality with procedural commands. In this article, we will discuss a program in PL/SQL to reverse a given number. Input : 98765 Output : 56789 Explanation : reverse number of 98765 is 56789. Input : 56784 Output : 48765 Explanation : Reverse number of '56784' is '48765'. Algorithm to Reverse a Number The algorithm to reverse a number involves extracting digits from the original number and building the reversed number step by step: Take out the last digit from the number ...
Read MoreSixth Normal Form (6NF)
In Sixth Normal Form (6NF), a relation variable is decomposed into its irreducible components − each table contains at most the primary key and one non-key attribute. A relation is in 6NF only if it is already in 5NF and every join dependency on the relation is trivial. 6NF represents the highest level of normalization, where we eliminate all possible redundancy by separating each non-key attribute into its own table. This extreme decomposition ensures that no information loss occurs during normalization while maintaining data integrity through join operations. Understanding 6NF Decomposition ...
Read MoreUnique Key in RDBMS
A Unique Key is a constraint in RDBMS that ensures all values in a column (or set of columns) are distinct. Many users confuse Primary Key with Unique Key since both enforce uniqueness, but they differ in NULL handling, volume, and modifiability. The unique key constraint is essential for maintaining data integrity by preventing duplicate entries while providing more flexibility than primary keys. It's commonly used for columns like email addresses, phone numbers, or social security numbers where uniqueness is required but the field may not serve as the primary identifier. Primary Key vs Unique Key Feature ...
Read MoreForeign Key in RDBMS
A Foreign Key is a column (or set of columns) in one table that creates a link to the primary key of another table. It establishes a relationship between two tables and enforces referential integrity − ensuring that values in the foreign key column always correspond to valid values in the referenced primary key. Example Consider two tables − Employee and Department. The DeptID in the Employee table is a foreign key that references the DeptID primary key in the Department table ? Employee EmpID (PK) EmpName EmpAge DeptID (FK) 1 ...
Read MoreAlternate Key in RDBMS
An Alternate Key (also called Secondary Key) is a candidate key that was not selected as the primary key. Every table may have multiple candidate keys that can uniquely identify each row, but only one is chosen as the primary key. The remaining candidate keys become alternate keys. Example 1: Student Table Consider the following Student table ? Student_ID Student_Enroll Student_Name Student_Email 096 2717 Manish aaa@gmail.com 055 2655 Manan abc@gmail.com 067 2699 Shreyas pqr@gmail.com Student_ID, Student_Enroll, and Student_Email are the candidate keys since each can uniquely ...
Read MoreCandidate Key in RDBMS
A Candidate Key is a minimal set of attributes that can uniquely identify each row in a table. Each table may have one or more candidate keys, and one of them is chosen as the Primary Key. A candidate key is essentially a minimal super key − no attribute can be removed from it without losing uniqueness. Example 1: Employee Table In an Employee table, both EmployeeID and EmployeeEmail can uniquely identify each employee. Therefore both are candidate keys. You select any one of them as the primary key, since a table can have only a single primary ...
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