A Gentle Introduction to

SQL


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SELECT within SELECT

This tutorial looks at how we can use SELECT statements within SELECT statements to perform more complex queries.

Exercises

Using nested SELECT.

1a List each country name where the population is larger than 'United States'.

1b List all details of countries in the regions containing 'Armenia', 'Iran'.

1c Show the European countries with a per capita GDP greater than 'United Kingdom'.

1d Which country has a population that is more than Kenya but less than Canada?

To get a well rounded view of the important features of SQL you should move on to the next tutorial concerning aggregates.

To gain an absurdly detailed view of one insignificant feature of the language, read on.

We can use the word ALL to allow >= or > or < or <=to act over a list.

2a Which countries have a GDP greater than any European country? [Give the name only.]

We can refer to values in the outer SELECT within the inner SELECT. We can name the tables so that we can tell the difference between the inner and outer versions.

3a Find the largest country in each region:

The following questions are very difficult:

3b Find the region for which all countries have a population of 0

3c Some countries have populations more than three times that of any of their nieghbours (in the same region). Give the countries and regions.