How to use SQL min() with float?

Question

I have the following database table:

 *Table structure for table `resultados` */
    DROP TABLE IF EXISTS `resultados`;

    CREATE TABLE `resultados` (

      `cpf` varchar(14) NOT NULL,
      `nome` varchar(255) DEFAULT NULL,
      `codcurso` int(5) DEFAULT NULL,
      `nota` float DEFAULT NULL,
      PRIMARY KEY (`cpf`)

);

/*Data for the table `resultados` */

insert  into `resultados`(`cpf`,`nome`,`codcurso`,`nota`) values 
('123.456.789-01','Alexandre Mie Lopes Mesa',78,4.21),
('123.876.332-72','Maria Ximenes Rosa',1,9.16),
('222.333.444-55','Livia Fernandes Linderberg',43,9.87),
('232.234.789-77','Karol Linderberg',43,8.92),
('289-890-912-76','Pedro Solano Susp',16,4.21),
('345.678.900-37','Amilton Pedro da Silva',78,9.98),
('432.654.987-21','Julio Martinez Silva',21,7.34),
('454.098.123-45','Luiz Henrique de Souza',1,7.35),
('765.123.098-22','Juliana Lopes Alves',22,5.67),
('903.201.871-23','Luiz Peres Lopes',16,8.77),
('987.654.321-10','Ana Alves de Souza',78,9.12);

And I want to select the minimum value, when I use only:

SELECT min(nota) AS menor FROM resultados

I get the result (4.21), but if I want to create a table, with students with lower grades I can’t get such a table

SELECT * FROM resultados WHERE nota = 4.21

I also tried to save this value as float and pass as var but it was not possible, I could only do with the following code:

SELECT * FROM resultados WHERE nota like '" + menorR + "'"

where less R = 4.21

Soon I want to understand why the Where note = (float number) did not work

Answer 1

This here works:

SELECT *
FROM resultados
WHERE nota = ( SELECT min(nota) AS menor
               FROM resultados )

Check on the Sqlfiddle: http://sqlfiddle.com/#! 2/6ebfe/4 (sometimes gets off the air for a while =( )

The problem is precision: He won’t find 4.210000038147 if you do only WHERE nota = 4.21.

---

As @Jorgeb. said well in the comments of the question, the ideal would be to use DECIMAL instead of FLOAT, because the DECIMAL you set the accuracy. For example: three house before the comma and two houses after the comma:

CREATE TABLE `resultados` (
  `cpf` varchar(14) NOT NULL,
  `nome` varchar(255) DEFAULT NULL,
  `codcurso` int(5) DEFAULT NULL,
  `nota` decimal(3, 2) DEFAULT NULL,
  PRIMARY KEY (`cpf`)
);

In decimal(3, 2), the first number shall be the boxes before the comma and the second the boxes after the comma.

Done this the version below should work (credits: @Jorgeb.):

SELECT * FROM resultados WHERE nota = 4.21