SQL

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.

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.

Constraints allow you to limit the type of data to insert into a table. These constraints can be specified when creating the table using the CREATE TABLE statement, or after creating the table using the ALTER TABLE statement. Constraints can be at the column or table level. Column level constraints are applied to only one column, while table level constraints apply to the entire table.

ALTER TABLE is the command used to add, delete or modify columns in an existing table. This command is also used to add and remove various constraints on an existing table.

In SQL to create a table you need to provide its name and its columns and the data type of each column. to delete a table definition as well as all the data, indexes, triggers, constraints and permission specifications for this table, we use the keyword DROP TABLE