Запити на видалення, оновлення, додавання даних

Summary

This practical lesson focuses on various database management operations, including creating backups, deleting records, updating data, and adding new entries. Students learn to use SQL queries to delete data about countries in Central and Eastern Asia, update population figures in Central and Eastern Europe, and create new tables based on specific conditions like area and population size. The session also covers how to insert new records into existing tables, such as adding countries starting with 'K'. The lesson emphasizes hands-on experience with different types of SQL queries for data manipulation and management.

Takeaways

• 😀 Backup your database by saving a copy with a new name and location before starting any operations.
• 😀 Create a delete query to remove records of countries in Central and Eastern Asia by filtering based on the 'Region' field.
• 😀 Use the 'Delete' query type when removing data, and ensure the deletion of the correct number of records.
• 😀 Update the population of countries in Central and Eastern Europe by increasing it by 15% using an 'Update' query.
• 😀 For the population update, multiply the population field by 1.15 (100% + 15%) to reflect the increase.
• 😀 Modify the area of Western European countries by increasing it by 1000 km² using an 'Update' query.
• 😀 Create a new table, 'Countries 1,' containing countries with an area greater than 1000 km² using the 'Create Table' query type.
• 😀 Use conditions like 'Area > 1000 km²' when creating the new table to filter the relevant data.
• 😀 Add countries starting with the letter 'K' to the 'Countries 1' table using an 'Insert' query with a condition on country names.
• 😀 Add countries whose names end with 'A' to the 'Countries 2' table by specifying this condition in the 'Insert' query.

Q & A

What is the primary task in the lesson described in the transcript?

The primary task is to automate data deletion, updating, and adding operations within a database.

What is the first step in starting the practical work with the database?

The first step is to create a backup of the existing database by saving it under a new name and location.

What is the purpose of creating a copy of the database in the lesson?

The purpose is to ensure data safety by working on a copy instead of the original database.

How do you create a query to delete countries from Central and Eastern Asia?

You use a 'delete' query, selecting the countries from the 'Countries' table that belong to the Central and Eastern Asia region, and specify the condition for deletion.

What is the process for updating the population of Central and Eastern European countries in the database?

To update the population, you create an 'update' query where the population field is multiplied by 1.15 to reflect a 15% increase.

How does the update query for population growth work?

The update query multiplies the population field by 1.15, which increases the population by 15%.

What is the correct syntax for the update query in the lesson to increase the population?

The syntax involves selecting the 'population' field and multiplying it by 1.15, with the condition specifying the region as Central and Eastern Europe.

What does the query for creating a new table (Countries 1) do?

The query creates a new table (Countries 1) and transfers records of countries whose areas are greater than 1000 square kilometers.

What is the purpose of the query that creates the 'Countries 2' table?

The 'Countries 2' table is created to store countries where the population is less than 5 million.

How does the query for adding data to the 'Countries 1' table work?

The 'add data' query adds countries to the 'Countries 1' table where the country name starts with the letter 'K' and populates the table with their name, capital, and area fields.