Difference between revisions of "SELECT Reference"

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{{SELECT Ref}}
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CREATE TABLE emp (ID NUMBER, name VARCHAR2(50));
The [[SELECT]] command is used to show data from a database.
 
 
 
The output from a SELECT statement is always a grid - with a number of rows and a number of columns.
 
==Simple SELECT==
 
The simplest SELECT commands involve a single table:
 
<source lang='sql'>
 
SELECT name, population
 
  FROM bbc
 
WHERE region='North America'
 
</source>
 
<table class="sqlmine"><tr><th>name</th><th>population</th></tr><tr><td>Canada</td><td class="r">32000000</td></tr><tr><td>Mexico</td><td class="r">106400000</td></tr><tr><td>United States of America</td><td class="r">295000000</td></tr></table>
 
*The SELECT line determines which columns to show - in this case <code>name</code> and <code>population</code>, both of which are columns of the bbc ta le.
 
*The WHERE clause determines which rows to show
 
 
 
The SELECT statement may involve data from more than one table using a [[JOIN]] or a [[UNION]].
 
 
 
SELECT statements may nested - that is the output from one SELECT may be the input to another SELECT.
 
 
 
The output from a SELECT may be added to another table using [[INSERT .. SELECT]]
 

Revision as of 11:00, 31 December 2012

CREATE TABLE emp (ID NUMBER, name VARCHAR2(50));