Difference between revisions of "SELECT"
From SQLZOO
(→Exercises) |
|||
| (26 intermediate revisions by 8 users not shown) | |||
| Line 1: | Line 1: | ||
| − | + | A SELECT statement gets data from a table. Each table contains rows and columns - you can SELECT some columns and ignore others | |
| − | + | *The column names on the select line control which columns you get | |
| − | <table | + | *The FROM clause controls which table you access |
| − | < | + | <div class=params>schema:scott</div> |
| − | < | + | The table <code>games</code> shows the year and the city hosting the Olympic Games. |
| − | + | <table border='1'> | |
| − | <th> | + | <caption>games</caption> |
| − | <th> | + | <tr> <th>yr</th> <th>city</th> <th>y1</th></tr> |
| − | </tr> | + | <tr> <td align='right'>2000</td> <td>Sydney</td> <td></td></tr> |
| − | <tr> | + | <tr> <td align='right'>2004</td> <td>Athens</td> <td>2000</td></tr> |
| − | + | <tr> <td align='right'>2008</td> <td>Beijing</td><td>2004</td> </tr> | |
| − | + | <tr> <td align='right'>2012</td> <td>London</td><td>2008</td> </tr> | |
| − | <td align='right'> | + | |
| − | <td | + | |
| − | <td></td> | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | + | ||
| − | + | ||
| − | <td align='right'> | + | |
| − | <td | + | |
| − | <td | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | + | ||
| − | + | ||
| − | <td align='right'> | + | |
| − | <td | + | |
| − | <td | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | + | ||
| − | + | ||
| − | <td align='right'> | + | |
| − | <td | + | |
| − | <td></td> | + | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | </tr> | + | |
</table> | </table> | ||
| − | = | + | <div class=qu> |
| − | + | The SELECT statement returns results from a <i>table</i>. | |
| − | + | In this example the table is <code>games</code> and the columns are | |
| − | < | + | <code>yr</code> and <code>city</code>. |
| − | + | <div class=tidy> | |
| − | + | DROP TABLE games; | |
| − | + | ||
| − | + | ||
| − | < | + | |
| − | + | ||
| − | </ | + | |
| − | + | ||
| − | < | + | |
| − | + | ||
| − | + | ||
</div> | </div> | ||
| + | <div class=setup> | ||
| + | CREATE TABLE games(yr INT, city VARCHAR(20),y1 INT); | ||
| + | INSERT INTO games(city,yr) VALUES ('Sydney',2000); | ||
| + | INSERT INTO games(city,yr,y1) VALUES ('Athens',2004,2000); | ||
| + | INSERT INTO games(city,yr,y1) VALUES ('Beijing',2008,2004); | ||
| + | INSERT INTO games(city,yr,y1) VALUES ('London',2012,2008); | ||
| + | </div> | ||
| + | <div class=def> | ||
| + | SELECT yr, city FROM games | ||
| + | </div> | ||
| + | </div> | ||
| + | |||
| + | ===See also:=== | ||
| + | *[[SELECT_basics | SELECT Tutorial]] - practice using the SELECT command | ||
| + | *[[SELECT_.._WHERE |SELECT ... WHERE]] - the WHERE clause allows you to get some rows but not others | ||
Revision as of 08:03, 3 January 2013
A SELECT statement gets data from a table. Each table contains rows and columns - you can SELECT some columns and ignore others
- The column names on the select line control which columns you get
- The FROM clause controls which table you access
schema:scott
The table games shows the year and the city hosting the Olympic Games.
| yr | city | y1 |
|---|---|---|
| 2000 | Sydney | |
| 2004 | Athens | 2000 |
| 2008 | Beijing | 2004 |
| 2012 | London | 2008 |
The SELECT statement returns results from a table.
In this example the table is games and the columns are
yr and city.
DROP TABLE games;
CREATE TABLE games(yr INT, city VARCHAR(20),y1 INT); INSERT INTO games(city,yr) VALUES ('Sydney',2000); INSERT INTO games(city,yr,y1) VALUES ('Athens',2004,2000); INSERT INTO games(city,yr,y1) VALUES ('Beijing',2008,2004); INSERT INTO games(city,yr,y1) VALUES ('London',2012,2008);
SELECT yr, city FROM games
See also:
- SELECT Tutorial - practice using the SELECT command
- SELECT ... WHERE - the WHERE clause allows you to get some rows but not others
