Difference between revisions of "SELECT .. SELECT"
From SQLZOO
| 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:
