Let's explore this database a bit further. The `country` database consists of a single table named `country`. Let's examine the contents of this table.

This table has **15 rows**, which means we have 15 distinct records for different countries.

Now, what about the columns? In this table, we have **7 columns**, like `id`,` name`, `continent`, `region`,
 `SurfaceArea`, `capital`, and `population`.

1. `id` - the record number in this table;

2. `name` - the name of the country;

3. `continent` - the name of the country's continent;

4. `region`- the name of the country's  region;

5. `SurfaceArea` - the total land area of the country;

6. `capital` - the capital of the country;

7. `population` - the population of the country.

 



We can also retrieve multiple columns with the `SELECT` operator. The only difference is that after the word `SELECT`, we will need to specify several column names, which must be **separated by commas**. Let’s take an example where we retrieve **three** columns from the country table:

In this section, we will learn how to use the SQL SELECT statement to get a single table column, multiple table columns, and all table columns. We will also find out how to return unique values.

In this section, we will learn how to sort retrieved data using the ORDER BY clause. This clause, which must be the last in the SELECT statement, can be used to sort data on one or more columns as needed.\n

In this section, we will learn how to filter returned data using the SELECT statement’s WHERE clause. We will learn how to test for equality, inequality, more and less significant than value ranges, and NULL values.

In this section, we will learn how to combine WHERE clauses with the AND and OR operators. We will also find out how the NOT operator works.\n\n\n

In this section, we will learn what the SQL aggregate functions are and how to use them to summarize table data.

You have a database that contains one table called Students. There are 3 columns in this table: student_id, student_mark, student_name. How can you get all the data from this table?

You have a database that contains one table called Students. There are 3 columns in this table: student_id, student_mark, student_name. How can you get only unique student names?

You have a database that contains one table called Students. There are 3 columns in this table: student_id, student_name, student_mark. How can I get the first five unique student names?

id	name	continent	region	surfacearea	capital	population
1	Japan	Asia	Eastern Asia	377829	Tokyo	126714000
2	Latvia	Europe	NULL	64589	Riga	2424200
3	Mexico	North America	Central America	1958201	Mexico City	98881000
...	...	...	...	...	...	...
15	Malta	Europe	Southern Europe	316	Valletta	380200

Introduction to SQL

Retrieving Multiple Columns

Task