SQL Database - Outro

What is a primary key in a SQL database?

• A primary key in a SQL database is a random number assigned to each record.

• A primary key in a SQL database is a secondary identifier for each record in a table.

• A primary key in a SQL database is a field that can have duplicate values.

• A primary key in a SQL database is a unique identifier for each record in a table.

Explain the purpose of foreign keys in a database.

• Foreign keys are used to increase the size of a database

• Foreign keys are used to link tables together and enforce referential integrity.

• Foreign keys are used for sorting data in a database

• Foreign keys are used to delete all records in a table

How can SQL be used to retrieve data from a database?

• Write SELECT queries with specified columns and conditions.

• Send a request to the database administrator

• Use HTML coding to retrieve data

• Access the database physically

Why is it important to have a primary key in a database table?

• To add redundancy to the data

• To improve query performance

• It is important to have a primary key in a database table to uniquely identify each record and ensure data integrity.

• To increase the table size

What is the role of foreign keys in maintaining data integrity?

• Foreign keys play a crucial role in maintaining data integrity by enforcing relationships between tables and ensuring referential consistency.

• Foreign keys are primarily used for data visualization.

• Foreign keys are only relevant for aesthetic purposes.

• Foreign keys are used for data encryption purposes.

Provide an example of a SQL query to join two tables.

• SELECT * FROM table1 JOIN table2 ON table1.id = table2.id;

• SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;

• SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.id;

• SELECT * FROM table1 WHERE table1.id = table2.id;

What is the purpose of the GROUP BY clause in SQL?

• The GROUP BY clause is used to sort the result set in ascending order.

• The GROUP BY clause is used to filter rows based on a specified condition.

• The GROUP BY clause is used to group rows that have the same values into summary rows.

• The GROUP BY clause is used to perform mathematical calculations on the result set.

Explain the difference between the WHERE and HAVING clauses in SQL.

• The WHERE clause is used to filter rows before grouping, while the HAVING clause is used to filter groups after grouping.

• The WHERE clause is used to filter rows after grouping, while the HAVING clause is used to filter rows before grouping.

• The WHERE clause is used to perform mathematical calculations, while the HAVING clause is used for data visualization.

• The WHERE clause is used to sort the result set, while the HAVING clause is used to perform joins.

What is the purpose of the ORDER BY clause in SQL?

• The ORDER BY clause is used to group rows based on a specified condition.

• The ORDER BY clause is used to filter rows before grouping.

• The ORDER BY clause is used to sort the result set based on one or more columns.

• The ORDER BY clause is used to perform mathematical calculations on the result set.