WHERE and HAVING clause are mainly used in the statement of SQL queries, these allow us to restrict the combination in the result relation through using a specific predicate. The major difference between WHERE and HAVING is that WHERE clause specifies the conditions for selecting the tuples (rows) from the relations, including join conditions if needed. On the other hand, HAVING clause specifies a condition on the groups being selected rather than on individual tuples. SQL stands for … [Read more...]

Data warehouse and Data mart are used as a data repository and serve the same purpose. These can be differentiated through the quantity of data or information they stores. The vital difference between a data warehouse and a data mart is that a data warehouse is a database that stores information-oriented to satisfy decision-making requests whereas data mart is complete logical subsets of an entire data warehouse. In simple words, a data mart is a data warehouse limited in scope and whose data … [Read more...]

Star and snowflake schemas are the most popular multidimensional data models used for a data warehouse. The crucial difference between Star schema and snowflake schema is that star schema does not use normalization whereas snowflake schema uses normalization to eliminate redundancy of data. Fact and dimension tables are essential requisites for creating schema. You can also refer our previously published article on the difference between fact and dimension table to understand it … [Read more...]

Data is raw, unanalyzed, unorganised, unrelated, uninterrupted material which is used to derive information, after analyzation. On the other hand, Information is perceivable, interpreted as a message in a particular manner, which provides meaning to data. Data doesn't interpret anything as it is a meaningless entity, while information is meaningful and relevant as well. Data and Information are different common terms which we frequently use, although there is a general interchangeability … [Read more...]

In this article, we will discuss two open source database management system i.e. MySQL and PostgreSQL.  Where MySQL is the product of Oracle Corporation and PostgreSQL is the product of Global Development Group. Which one is best to use? The answer to this question varies from programmer to programmer. This depends on the requirement of the application or website that a programmer is creating. Both MySQL and PostgreSQL differ in many aspects. Let us discuss the differences between MySQL and … [Read more...]

So far, we have talked about original tables stored in the physical form in databases. In which we have access to all the attributes of the tables. What if we have to restrict a user from accessing some attributes of the table and let access the other attributes. Like, a clerk in an administrative department can search the name, address, designation, age and such other factors of an employee table. But he must not be authorized to view or access the salary of any employee. In such cases, we … [Read more...]

Talking about the Strong and Weak entity, we must know what does an entity means. An entity is a unique object in the real world. It is described as the set of attributes. The collection of the same type of entities together forms the entity set. Here, we will discuss two types of entities Strong entity and Weak entity. The weak entity always depends on the strong entity for its existence. Let us discuss the differences between both, the Strong entity and weak entity with the help of comparison … [Read more...]

Keys are the essential elements of any relational database. It identifies each tuple in a relation uniquely. Keys are also used to establish the relationship among the tables in a schema. In this article, we will discuss two basic keys of any database that is super key and candidate key. Every candidate key is a super key but, every super key may or may not be a candidate key. There many other distinguishing factors between super key and candidate key, which I have briefly discussed in the … [Read more...]

Relational Algebra and Relational Calculus are the formal query languages for a relational model. Both form the base for the SQL language which is used in most of the relational DBMSs. Relational Algebra is a procedural language. On the other hands, Relational Calculus is a declarative language. Relational Algebra and Relational Calculus can be further differentiated on many aspects, which I have discussed below with the help of comparison chart. Content: Relational Algebra Vs Relational … [Read more...]

OLAP is a common term between ROLAP and MOLAP which stands for Online Analytical Processing. OLAP is a specialized tool that creates a multidimensional view of data for the user to do the analysis. ROLAP and MOLAP are two models of OLAP. Though they are different in many aspects, the most important difference between them is ROLAP provides data, directly from main data warehouse whereas, MOLAP provides data from the proprietary databases MDDBs. Let us view some more differences between ROLAP … [Read more...]