Difference between revisions of "SELECT Reference"
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<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> | <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> | ||
</td></tr></table> | </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 | + | *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 table. |
*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]]. | |
| − | 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]] | |
| − | 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]] | + | |
Latest revision as of 12:48, 18 June 2013
SELECT Operations
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.
[edit] Simple SELECT
The simplest SELECT commands involve a single table:
| SQL | Result | ||||||||
|---|---|---|---|---|---|---|---|---|---|
SELECT name, population FROM bbc WHERE region='North America' |
|
- The SELECT line determines which columns to show - in this case
nameandpopulation, both of which are columns of the bbc table. - 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
