Databases

This is the third set of solved exercises to master the use of select, GROUP BY, HAVING, INTERSECT

This is the third set of solved exercises to master the use of select, GROUP BY, HAVING, INTERSECT

This is the third set of solved exercises to master the use of select, GROUP BY, HAVING, INTERSECT

Given the database called "project_management" allowing to manage projects related to software development. It is described by the following simplified text representation:

given the database of a music festival: In one performance can participate one or more musicians. A musician can only participate in one performance.

Once the analysis is complete, the next step is to develop a series of models, based on the analysis document. These models will allow us later to implement a database, which will contain all the information necessary for the proper functioning of the computerized system.

An information system does not necessarily have to be computerized. Although most of today's systems are based on computer technology, there are still information systems where information is stored, manipulated and communicated using "traditional" means such as cupboards, filing cabinets, calculators, paper charts, etc.

The competitiveness of a company and its value on the market are determined by several elements, of different importance depending on the sector of activity. We can generally group these elements into two classes

SELECT is the most commonly used statement in SQL. The SELECT statement in SQL is used to extract data from a database. We can recover the entire table or according to certain specified rules. The returned data is stored in a results table. This result table is also called a result set.

The INSERT INTO statement is used to add new rows of data to a table in the database. The UPDATE query is used to modify existing records in a table. You can use the WHERE clause with the UPDATE query to update the selected rows, otherwise all the rows would be affected.