Note: This is an RHCE 7 exam objective.
Prerequisites
First, you need to install a MariaDB database.
Then, you have to create a simple database schema.
Initial Connection
Now, you need to connect to your database (here called test):
# mysql -u user -p test Enter password:your passwordReading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 18 Server version: 5.5.35-MariaDB MariaDB Server Copyright (c) 2000, 2013, Oracle, Monty Program Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [test]>
You can check the presence of the table, previously created, called addresses:
MariaDB [test]> desc addresses; +---------+------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+------------------+------+-----+---------+-------+ | id | int(10) unsigned | YES | | NULL | | | name | varchar(20) | YES | | NULL | | | address | varchar(40) | YES | | NULL | | +---------+------------------+------+-----+---------+-------+ 3 rows in set (0.00 sec)
Data Insertion
You can insert some data into the table called addresses:
MariaDB [test]> insert addresses values(1,"James","address1"); Query OK, 1 row affected (0.02 sec) MariaDB [test]> insert addresses values(2,"Bill","address2"); Query OK, 1 row affected (0.02 sec)
Data Selection
Now, you can get James‘ address:
MariaDB [test]> select address from addresses where name="James"; +----------+ | address | +----------+ | address1 | +----------+ 1 row in set (0.00 sec)
You can also get all the records ordered by name in an ascending order (ASC is the default order and can be omitted):
MariaDB [test]> select * from addresses order by name ASC; +------+-------+----------+ | id | name | address | +------+-------+----------+ | 2 | Bill | address2 | | 1 | James | address1 | +------+-------+----------+ 2 rows in set (0.00 sec)
Data Update
You can replace the name “Bill” with “John“:
MariaDB [test]> update addresses set name="John" where name="Bill"; Query OK, 1 row affected (0.02 sec) Rows matched: 1 Changed: 1 Warnings: 0 MariaDB [test]> select * from addresses order by name DESC; +------+-------+----------+ | id | name | address | +------+-------+----------+ | 2 | John | address2 | | 1 | James | address1 | +------+-------+----------+ 2 rows in set (0.00 sec)
Note: DESC specifies a descending order.
Data Removal
You can also delete James‘ record:
MariaDB [test]> delete from addresses where name="James"; Query OK, 1 row affected (0.02 sec) MariaDB [test]> select * from addresses; +------+------+----------+ | id | name | address | +------+------+----------+ | 2 | John | address2 | +------+------+----------+ 1 row in set (0.00 sec)
This is a very basic tutorial. A lot of other operations are available for a database software like MariaDB. A complete documentation can be found on the MySQL website.
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