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Articles by AmitDiwan
Page 680 of 840
Difference Between ALTER and UPDATE Command in SQL
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 MoreDifference Between ROLAP and MOLAP
In this post, we will understand the difference between ROLAP and MOLAP.ROLAPIt stands for Relational Online Analytical Processing.It is used for large volumes of data.The access time in ROLAP is slow.It stores data in the form of relation tables.The data in ROLAP is fetched from a data warehouse.It uses complex SQL queries.A static multidimensional view of the data is created in ROLAP.MOLAPIt stands for Multidimensional Online Analytical Processing.It is used for less/limited volumes of data.The access time is quick in MOLAP.Data is stored in a multidimensional array.Data is fetched from the MDDBs database.A sparse matrix is used in MOLAP.Dynamic multidimensional ...
Read MoreDifference Between Strong and Weak Entity
In this post, we will understand the difference between strong entity and weak entity −Strong EntityIt has primary key.It doesn’t depend on any other entity.It can be represented using a single rectangle.The relationship between two strong entities can be represented using a single diamond.It can either have total participation or no participation.Weak EntityA weak entity has a partial discriminator key.It depends on the strong entity.It can be represented using a double rectangle.The relationship between a strong and a weak entity can be represented using a double diamond.They always have total participation.
Read MoreDifference Between Star and Snowflake Schema
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 MoreDifference Between 3NF and BCNF
In this post, we will understand the difference between 3NF and BCNF.3NFThere shouldn’t be any transitive dependency.There shouldn’t be any non-prime attribute that depends transitively on a candidate key.It is not as strong as BCNF.It has high redundancy.The functional dependencies are already present in INF and 2NF.It is easy to achieve.It can be used to achieve lossless decomposition.BCNFFor any relation A->B, ‘A’ should be a super key of that specific relation.It is stronger than 3NF.The functional dependencies are present in 1NF, 2NF and 3NF.It has low redundancy in comparison to 3NF.The functional dependencies may or may not be preserved.It is ...
Read MoreDifference Between MySQL and PostgreSQL
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 MoreDifference Between T-SQL and PL-SQL
In this post, we will understand the difference between T-SQL and PL-SQL.T-SQLIt is a Microsoft product.It is known as Transact Structure Query language.It gives a high degree of control to the developers/programmers.It works its best, and provides good performance with Microsoft SQL server.It is easy.It is simple to understand.It allows the insertion of multiple rows into a table.This is done with the help of the ‘BULK INSERT’ statement.The ‘SELECT INTO’ statement is used in T-SQLIn this, the ‘NOT EXISTS’ clause can be used with the ‘SELECT’ statements.PL-SQLIt is an Oracle product.It is known as Procedural Language Structural Query Language.It is ...
Read MoreDifference Between Linear and Logistic Regression
In this post, we will understand the difference between linear regression and logistic regression.Linear RegressionIt helps predict the variable that is continuous, and is a dependent variable.This is done using a given set of independent variables.It extrapolates a line to find the value of dependent variable.Least square methods are used to estimate the accuracy.The best fit line is found, that helps predict the output.It is generally a continuous value.The relation between the dependent variable and independent variable has to be linear.The independent variables may have collinearity between them.It is considered a machine learning problem, i.e an applied statistics problem.Logistic RegressionIt ...
Read MoreDifference Between Grant and Revoke
In this post, we will understand the difference between grant and revoke.GrantIt is a DCL command.It grants permissions to users on database objects.It can also be used to assign access rights to users.For every user, the permissions need to be specified.When the access is decentralized, permission granting is easier.Syntax:grant privilege_name on object_name to {user_name | public | role_name}RevokeIt is a DCL command.It removes permissions if they are granted to users on database objects.It takes away/revokes the rights of the users.If access for a user is removed, all specific permissions provided by that user to others will be removed.If decentralized access ...
Read MoreDifference Between SQL and T-SQL
In this post, we will understand the difference between SQL and T-SQL.SQLIt is a non-procedural language.Relational databases use SQL.It stands for structured query language.It uses query to view and manipulate data.DML and DDL operations are used- Data manipulation language, and data definition language.It is considered as an open-source language.It helps in the manipulation of data and data controlling.Transfer of data happens one by one when SQL is used.T-SQLIt is a Microsoft product.It is known as Transact Structure Query language.It gives a high degree of control to the developers/programmers.It works its best, and provides good performance with Microsoft SQL server.It is ...
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