Difference between revisions of "SELECT Reference"
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The output from a SELECT statement is always a grid - with a number of rows and a number of columns. | 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: | The simplest SELECT commands involve a single table: | ||
<source lang='sql'> | <source lang='sql'> | ||
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WHERE region='North America' | WHERE region='North America' | ||
</source> | </source> | ||
<table class="sqlmine" | <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 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 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 10:12, 11 August 2012
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:
SELECT name, population
FROM bbc
WHERE region='North America'
| name | population |
|---|---|
| Canada | 32000000 |
| Mexico | 106400000 |
| United States of America | 295000000 |
- The SELECT line determines which columns to show - in this case
nameandpopulation, 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