CIA World Factbook

Using nested select statements

The result of a SELECT statement may be used as a value in another statement. For example the statement SELECT region FROM cia WHERE name = 'Brazil' evaluates to 'South America' so we can use this value to obtain a list of all countries in the same region as 'Brazil'

SELECT name FROM cia WHERE region = 
  (SELECT region FROM cia WHERE name = 'Brazil')

Note that this is not the same thing as a join.

Observe the tables which result from each of the following

• SELECT name FROM cia
     WHERE region = (SELECT region FROM cia WHERE name = 'Belarus')

  
  The countries in the same region as Belarus.

  name
  Armenia
  Azerbaijan
  Belarus
  Moldova
  Ukraine