For understanding the information domain of a problem, there are two data modelling concepts, namely, cardinality and modality. Cardinality and modality are very important for analyzing the data objects, attributes, and relationship structures. The most basic difference between cardinality and modality is that the cardinality is a metric that specifies the number of occurrences of a data object with respect to the number of occurrences of another data object, whereas, the modality specifies whether a data object must participate in a relationship or not. In this article, we will discuss the important differences between cardinality and modality. Let's start with ... Read More

RAID or Redundant Array of Independent Disk is a set of disk organization techniques developed to increase the reliability and performance of a system. There are various types of RAID techniques such as RAID 0, RAID 1, RAID 2, … RAID 5. Read this article to learn more about RAID 0 and RAID 1 and how they are different from each other. What is RAID 0? RAID 0 stands for Redundant Array of Independent Disk level 0. There is no redundant data stored here, so performance is very good. But the failure of any disk in the array results in loss of data. In RAID 0, ... Read More

In this post, we will understand the difference between trigger and a procedure.TriggersIt is implicitly invoked when an event such as INSERT, DELETE, and UPDATE occurs in a table of a database.Nesting of triggers can be achieved using a table.A trigger can’t be called or defined inside another trigger.Transactional statements such as ‘COMMIT’, ‘ROLLBACK’, ‘SAVEPOINT’ can’t be used in triggers.They are used to maintain referential integrity.This is done by keeping a record of the activities performed on a table.No values are returned in a trigger.No value can be passed as a parameter to a trigger.Syntax to define a trigger:CREATE TRIGGER ... Read More

In this post, we will understand the difference between the ALTER command and the UPDATE command in SQL.ALTER CommandThis command is a Data Definition Language (DDL).It performs operation at the structural level, not the data level.This command is used to add, delete, and modify the attributes of the tables in a database.This command, by default, initializes the values of all values in the tuple to NULL.It changes the structure of the table.Syntax: Add a column −ALTER TABLE table_name ADD column_name datatype;Drop a ColumnALTER TABLE table_name DROP COLUMN column_name;UPDATE CommandThis command is a Data Manipulation Language (DML).It performs operations on the ... Read More

In this post, we will understand the difference between star schema and snowflake schema.Star SchemaHierarchies of dimensions are stored in a dimensional table.It contains a fact table that is surrounded by dimension tables.In this schema, a single join creates the relationship between a fact table and any dimension tables.It is a simple database design.It has high levels of data redundancy.The processing of cube is quick.A single dimension table contains the aggregated data.It is a de-normalized data structure.The queries run quickly in comparison to other schema.It uses start join query optimization technique. Hence, the queries perform well.Tables can be connected with ... Read More

In computer science and information technology, the terms data and information are frequently used as if they are synonyms, but in reality, they are quite different from each other. The most fundamental difference between the two is that data is the collection of raw facts and figures, while information is the processed data that have a meaning for a user. Read this article to find out more about "data" and "information" and how these two terms are different from each other. What is Data? Data is a collection of raw facts and figures that can be processed by any computing ... Read More

In this post, we will understand the difference between MySQL and PostgreSQL.MySQLIt is a relational database management system.It is the product developed by Oracle Corporation.It is supported by Windows, Mac OS X, Linux, BSD, UNIX, z/OS, Symbian, AmigaOS.It can’t be extended.In this system, the phpMyAdmin tool gives the GUI.Mysqldump and XtraBackup provide backup in MySQL.It provides temporary table.It doesn’t provide a materialized view.It doesn’t provide Data Domain Object to the system.PostgreSQLIt is an object-relational database management system.It was developed by the Global Development Group.It is supported by Windows, Mac OS X, Linux and BSD but not by UNIX, z/OS, Symbian, ... Read More

In this post, we will understand the difference between WHERE clause and HAVING clause in SQL.WHERE ClauseIt is used to filter the records from the table based on a specific condition.It can be used without the ‘GROUP BY’ clause.It can be used with row operations.It can’t contain the aggregate functions.It can be used with the ‘SELECT’, ‘UPDATE’, and ‘DELETE’ statements.It is used before the ‘GROUP BY’ clause if required.It is used with a single row function such as ‘UPPER’, ‘LOWER’.HAVING ClauseIt is used to filter out records from the groups based on a specific condition.It can’t be used without the ... Read More

DELETE is a Data Manipulation Language (DML) command. It is used to remove tuples/records from a relation/table. On the other hand, DROP is a Data Definition Language (DDL) command and is used to remove named elements of schema like relations/table, constraints or entire schema. Read this article to learn more about DELETE and DROP commands in SQL and how they are different from each other. What is DELETE in SQL? In SQL, the DELETE command is used to remove some or all the records from a database table. With the DELETE command, the WHERE clause is used to define the ... Read More

In this post, we will understand the difference between COMMIT and ROLLBACK in SQL.COMMITIt validates the modifications that are made by the current transaction.Once the COMMIT statement has been executed, the transaction can’t be rolled back using ROLLBACK.It occurs when the transaction is successfully executed.SyntaxCOMMIT;ROLLBACKIt removes the modifications that were made by the current transaction.Once ROLLBACK is executed, the database would reach its previous state.This is the state where the first statement of the transaction would be in execution.ROLLBACK happens when the transaction is aborted in between its execution.SyntaxROLLBACK;