SELECT .. SELECT

Subquery Table, Derived Tables, Nested Queries

You can use the results from one query in another query

You may use a SELECT statement in the FROM line SELECT f FROM (SELECT ). In this case the derived table X has columns name and gdp_per_capita. The calculated values in the inner SELECT can be used in the outer SELECT.

SELECT name, ROUND(gdp_per_capita)
  FROM
  (SELECT name,
          gdp/population AS gdp_per_capita
     FROM bbc) X
 WHERE gdp_per_capita>20000

Notice that

• the inner table is given an alias X
• the first column in the inner query keeps its name
• the second column in the inner query has an alias

Find the countries in the same region as Butan

You may use a SELECT statement in the WHERE line - this returns a list of regions.

SELECT name
  FROM bbc
 WHERE region IN
  (SELECT region FROM bbc
    WHERE name='Butan')

See also:

• SELECT in SELECT Tutorial
• SELECT JOIN