MariaDB [(none)]> create database seguridad;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> use seguridad;
Database changed
MariaDB [seguridad]> create table usuario
    -> (nombre char(20) not null,
    -> clave char(10)0 not null);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '0 not null)' at line 3
MariaDB [seguridad]> create table usuario
    -> (nombre char(20) not null,
    -> clave char(10) not null);
Query OK, 0 rows affected (0.14 sec)

MariaDB [seguridad]> describe usuario;
+--------+----------+------+-----+---------+-------+
| Field  | Type     | Null | Key | Default | Extra |
+--------+----------+------+-----+---------+-------+
| nombre | char(20) | NO   |     | NULL    |       |
| clave  | char(10) | NO   |     | NULL    |       |
+--------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)

MariaDB [seguridad]> select encode('triste','dia');
+------------------------+
| encode('triste','dia') |
+------------------------+
| Õsv¾ÀÈ                 |
+------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> insert into usuario value('Mauricio Vasquez',encode('mao','123'));
Query OK, 1 row affected (0.06 sec)

MariaDB [seguridad]> select * from usuario;
+------------------+-------+
| nombre           | clave |
+------------------+-------+
| Mauricio Vasquez | ?z'   |
+------------------+-------+
1 row in set (0.00 sec)

MariaDB [seguridad]> insert into usuario value('Javier Ospina',encode('jom','456'));
Query OK, 1 row affected (0.03 sec)

MariaDB [seguridad]> select * from usuario;
+------------------+-------+
| nombre           | clave |
+------------------+-------+
| Mauricio Vasquez | ?z'   |
| Javier Ospina    | }}   |
+------------------+-------+
2 rows in set (0.00 sec)

MariaDB [seguridad]> select @clave:=encode('sol','145');
+-----------------------------+
| @clave:=encode('sol','145') |
+-----------------------------+
| ¢×                         |
+-----------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> insert into usuario value('Sol Mireya',@clave);
Query OK, 1 row affected (0.04 sec)

MariaDB [seguridad]> select * from usuario;
+------------------+-------+
| nombre           | clave |
+------------------+-------+
| Mauricio Vasquez | ?z'   |
| Javier Ospina    | }}   |
| Sol Mireya       | ½ž   |
+------------------+-------+
3 rows in set (0.00 sec)

MariaDB [seguridad]> select decode(clave,'123') from usuario where nombre='Mauricio Vasquez';
+---------------------+
| decode(clave,'123') |
+---------------------+
| mao                 |
+---------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select decode(clave,'jom') from usuario where nombre='Javier Ospina';
+---------------------+
| decode(clave,'jom') |
+---------------------+
| >b                 |
+---------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select decode(clave,'456') from usuario where nombre='Javier Ospina';
+---------------------+
| decode(clave,'456') |
+---------------------+
| jom                 |
+---------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select decode(clave,'145') from usuario where nombre='Sol Mireya;
    '> '
    -> ;
Empty set (0.00 sec)

MariaDB [seguridad]> select decode(clave,'145') from usuario where nombre='Sol Mireya';
+---------------------+
| decode(clave,'145') |
+---------------------+
| sol                 |
+---------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select locate('r','sergio se rie mucho');
+-----------------------------------+
| locate('r','sergio se rie mucho') |
+-----------------------------------+
|                                 3 |
+-----------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select locate('s',sergio se rie mucho');
    '> '
    -> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'rie mucho');
'' at line 1
MariaDB [seguridad]> select locate('s','sergio se rie mucho');
+-----------------------------------+
| locate('s','sergio se rie mucho') |
+-----------------------------------+
|                                 1 |
+-----------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select position('i' in 'sergio se rie mucho'),
    -> '
    '> ;
    '> ;
    '> '
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> 
    -> ,;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 19
MariaDB [seguridad]> select position('i' in 'sergio se rie mucho');
+----------------------------------------+
| position('i' in 'sergio se rie mucho') |
+----------------------------------------+
|                                      5 |
+----------------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select position('h' in 'sergio se rie mucho');
+----------------------------------------+
| position('h' in 'sergio se rie mucho') |
+----------------------------------------+
|                                     18 |
+----------------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select mid('hola como estas' from 4 for 6);
+-------------------------------------+
| mid('hola como estas' from 4 for 6) |
+-------------------------------------+
| a como                              |
+-------------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select ltrim('     estudien chicos     ');
+------------------------------------+
| ltrim('     estudien chicos     ') |
+------------------------------------+
| estudien chicos                    |
+------------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select rtrim('     estudien chicos     ');
+------------------------------------+
| rtrim('     estudien chicos     ') |
+------------------------------------+
|      estudien chicos               |
+------------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> select trim('     estudien chicos     ');
+-----------------------------------+
| trim('     estudien chicos     ') |
+-----------------------------------+
| estudien chicos                   |
+-----------------------------------+
1 row in set (0.00 sec)

MariaDB [seguridad]> exit