Creating a Database with Perl and DBI - The SELECT Command
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The SELECT command allows us to query the database, and it reports back to us the information that matches the criteria we specify from the table we indicate. We have seen severalSELECTcommands in this form:

mysql> SELECT * FROM musicians; 

player_id	name	phone
1	Roger Waters	555-1212
2	Geddy Lee	555-2323
3	Marshall Mathers III	555-3434
4	Thom Yorke	555-4545
5	Lenny Kravitz	555-5656
6	Mike Diamond	555-6767

 

6 rows in set (0.00 sec)

ThisSELECTasks for*from the table namedmusicians. The*means “all fields” in the order that they are in the table. We can explicitly ask for the fields by listing them comma separated instead of using the star.

mysql> SELECT player_id, name, phone FROM musicians;

player_id	name	phone
1	Roger Waters	555-1212
2	Geddy Lee	555-2323
3	Marshall Mathers III	555-3434
4	Thom Yorke	555-4545
5	Lenny Kravitz	555-5656
6	Mike Diamond	555-6767

6 rows in set (0.01 sec)

The fields we select can be in any order.

mysql> SELECT name, phone, player_id FROM musicians;

name	phone	player_id
Roger Waters	555-1212	1
Geddy Lee	555-2323	2
Marshall Mathers III	555-3434	3
Thom Yorke	555-4545	4
Lenny Kravitz	555-5656	5
Mike Diamond	555-6767	6

6 rows in set (0.00 sec)

We can request specific fields—we don’t need to show all the fields available.

mysql> SELECT name, phone FROM musicians;
+----------------------+----------+
| name                 | phone    |
+----------------------+----------+
| Roger Waters         | 555-1212 |
| Geddy Lee            | 555-2323 |
| Marshall Mathers III | 555-3434 |
| Thom Yorke           | 555-4545 |
| Lenny Kravitz        | 555-5656 |
| Mike Diamond         | 555-6767 |
+----------------------+----------+
6 rows in set (0.00 sec)

Please check back next week for the continuation of this article.

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