Compare if there is already a record in BD MySql

Well, come on.

First, your table has serious structuring problems, you do not save (at least on this table) at any time what the customer is booking, and also saves the final / initial time and minute in 4 columns when you can easily use only 2 columns DATETIME , then restructured your table, it would look like this:

+-----------------+--------------+------+-----+-------------------+----------------+
| Field           | Type         | Null | Key | Default           | Extra          |
+-----------------+--------------+------+-----+-------------------+----------------+
| reserva_id      | smallint(6)  | NO   | PRI | NULL              | auto_increment |
| cliente         | varchar(100) | NO   |     | NULL              |                |
| sala            | smallint(3)  | NO   |     | NULL              |
| reservado_em    | timestamp    | NO   |     | CURRENT_TIMESTAMP |                |
| datahora_inicio | datetime     | NO   |     | NULL              |                |
| datahora_fim    | datetime     | NO   |     | NULL              |                |
+-----------------+--------------+------+-----+-------------------+----------------+

* Note that the cliente field is text, ideally you should change this field to cliente_id and set a foreign key.

Code CREATE of table:

CREATE TABLE 'reservas' (
	'reserva_id' SMALLINT(6) NOT NULL AUTO_INCREMENT,
	'cliente' VARCHAR(100) NOT NULL,
	'sala' SMALLINT(3) NOT NULL,
	'reservado_em' TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
	'datahora_inicio' DATETIME NOT NULL,
	'datahora_fim' DATETIME NOT NULL,
	PRIMARY KEY ('reserva_id')
)
ENGINE=InnoDB
AUTO_INCREMENT=6
;

In this way, you can register a reservation using:

insert into reservas(cliente, sala, datahora_inicio, datahora_fim) values('José', 001, '2015-05-25 11:00:00', '2015-05-25 11:59:59');

So you can check if the time chosen by the customer trying to make a reservation is already reserved using:

select * 
  from reservas 
 where (
            (datahora_inicio between '2015-05-25 11:00:00' and '2015-05-25 11:59:59') or
            (datahora_fim between '2015-05-25 11:00:00' and '2015-05-25 11:59:59')
         )
   and sala = 1;

See the example in SQLFiddle for you to test queries.

SELECT count(*) FROM agenda WHERE agenda_sala = <id_da_sala> AND agenda_hora_inicial = <hora_inicial> AND agenda_hora_final = <hora_final> AND agenda_data_inicial = <data_inicial> AND agenda_data_final = <data_final>;

If you return 0, it is because you do not have any scheduling for that room, at the time and date stipulated.