Difference between revisions of "SELECT .. SELECT"
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Line 3: | Line 3: | ||
<div class='qu'> | <div class='qu'> | ||
You may use a SELECT statement in the FROM line. | You may use a SELECT statement in the FROM line. | ||
In this | In this case the derived table X has columns <code>name</code>, | ||
<code>region</code> and <code>gdp_per_capita</code> | |||
<source lang='sql' class='def'> | <source lang='sql' class='def'> | ||
SELECT name, | SELECT name, ROUND(gdp_per_capita) | ||
FROM | FROM | ||
(SELECT name, gdp/population AS gdp_per_capita | (SELECT name,region, | ||
gdp/population AS gdp_per_capita | |||
FROM bbc) X | FROM bbc) X | ||
WHERE region='North America' | |||
</source> | </source> | ||
</div> | </div> |
Revision as of 23:39, 8 August 2012
The Derived Table (SELECT FROM SELECT)
You can use the results from one query in another query
You may use a SELECT statement in the FROM line.
In this case the derived table X has columns name
,
region
and gdp_per_capita
SELECT name, ROUND(gdp_per_capita)
FROM
(SELECT name,region,
gdp/population AS gdp_per_capita
FROM bbc) X
WHERE region='North America'
What about ties?
If one region has two countries with the same, highest population then the query will produce the right answers but there will be duplication- both countries will be shown.
See also: