Introduction to Group By  >>>

Scenario world

See details on the model

In this scenario, we have a single table world in which each row describes a country. The table contains the following attributes:

  • name of type VARCHAR(50) NOT NULL, the name of the country (e.g. France)
  • continent of type VARCHAR(60), in which continent is the country in (e.g. Europe)
  • area of time DECIMAL(10) the area of the country in square kilometer
  • population of type DECIMAL(11) the number of inhabitants
  • gdp of type DECIMAL(14) the Gross Domestic Product
  • capital of type VARCHAR(60) the name of the capital city
  • tld of type VARCHAR(5) the Top Level Domain of the country (the last part of the domain names of the country, e.g. .fr for France)
  • flag of type VARCHAR(255) an url of the flag of the country

Question

Compute the total population of each continent

Interaction between GROUP BY and WHERE

The group by is performed after the joins and the conditions in the WHERE have been checked. If we want to impose a condition on the result of the GROUP BY we can use HAVING that is similar to the WHERE but is applied other the result of the GROUP BY.

Query


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