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RDBMS Articles
Page 6 of 8
Multiversion Concurrency Control Techniques
This article has a truncated Drawbacks section at the end. Let me fix that and clean up the SVGs: It is essential to maintain data consistency and prevent concurrency issues in database systems when multiple transactions access the same data simultaneously. Multiversion Concurrency Control (MVCC) techniques provide an efficient way to achieve this by maintaining multiple versions of data items. Concurrency Control Protocols Database systems provide concurrency control to ensure isolation among transactions, maintain consistency, and resolve conflicts arising from read−write and write−read operations. The main techniques used are − Two−phase locking protocol Timestamp ordering ...
Read MoreCount odd and even digits in a number in PL/SQL
We are given a positive integer of digits and the task is to calculate the count of odd and even digits in a number using PL/SQL. PL/SQL is a combination of SQL along with the procedural features of programming languages. It was developed by Oracle Corporation in the early 90's to enhance the capabilities of SQL. PL/SQL is one of three key programming languages embedded in the Oracle Database, along with SQL itself and Java. Input int number = 23146579 Output count of odd digits in a number are : 5 count of even digits in a number are : ...
Read MoreDifference between Primary key and Foreign key in Database
In a relational database, keys are the most important elements to maintain the relationship between two tables or to uniquely identify the data from a table. Primary key is used to identify data uniquely therefore two rows can't have the same primary key. It can't be null. On the other hand, foreign key is used to maintain relationship between two tables. The primary key of a table acts as the foreign key in another table. The Foreign key in a table helps enforce Referential Integrity constraint. Read this tutorial to find out more about Primary and Foreign keys and ...
Read MoreDifference between Function and Procedure
SQL (Structured Query Language) is a computer language which is used to interact with an RDBMS (Relational Database Management System). It is basically a method of managing, organizing, and retrieving data from a relational database. In SQL, two important concepts are used namely, function and procedure. A function calculates the results of a program based on the inputs provided, whereas a procedure is used to perform some tasks in a specific order. There are many other differences between functions and procedures, which we will discuss in this article. What is Function? A function, in the context of ...
Read MoreVarious Types of Keys in DBMS
The different types of keys in DBMS are − Candidate Key − The candidate keys in a table are defined as the set of keys that is minimal and can uniquely identify any data row in the table. Primary Key − The primary key is selected from one of the candidate keys and becomes the identifying key of a table. It can uniquely identify any data row of the table. ...
Read MoreBinary 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 ...
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