I get the error: incorrect table definition [duplicate] - mysql

Question

This question already has answers here:
There can be only one auto column
(6 answers)
Closed 2 years ago.
Im using phpmyadmin for the first time and I get this error: incorrect table definition. there can be only one auto column and it must be defined as key. What am I doing wrong?
This is my code:
CREATE TABLE `database_reservering`.`formData` (
`nameTeacher` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`nameChild` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL , `email` VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`age` INT(11) NOT NULL ,
`date` DATE NOT NULL ,
`comment` VARCHAR(300) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`id` INT(30) UNSIGNED NOT NULL AUTO_INCREMENT ,
PRIMARY KEY (`nameTeacher`)
) ENGINE = InnoDB;

Answer 1

The actual error message is:
Incorrect table definition; there can be only one auto column and it must be defined as a key
The problem is that you have id as auto-increment, but the primary key is on nameTeacher. This is not allowed. You can change the statement to make id the primary key, and put a unique constraint on nameTeacher. This implements the same logic, but is valid MySQL syntax:
CREATE TABLE `formData` (
...
PRIMARY KEY (`id`),
UNIQUE (`nameTeacher`)
) ENGINE = InnoDB;
Demo on DB Fiddle

Answer 2

Change
PRIMARY KEY (nameTeacher)
to
PRIMARY KEY (id)
Full statement:
CREATE TABLE formData (
nameTeacher VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
nameChild VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
email VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
age INT(11) NOT NULL ,
`date` DATE NOT NULL ,
`comment` VARCHAR(300) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
id INT UNSIGNED NOT NULL AUTO_INCREMENT ,
PRIMARY KEY (id)) ENGINE = InnoDB;

Answer 3

What do you want to achieve when PK is set to the column other than AUTO_INCREMENT?
If you want to have separate independent autoincremented sequence for each nameTeacher value then alter the engine to MyISAM and define PK like (nameTeacher, id):
CREATE TABLE `formData` (
`nameTeacher` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`nameChild` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`email` VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`age` INT(11) NOT NULL , `date` DATE NOT NULL ,
`comment` VARCHAR(300) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`id` INT(30) UNSIGNED NOT NULL AUTO_INCREMENT ,
PRIMARY KEY (`nameTeacher`, `id`)
) ENGINE = MyISAM;
fiddle
See Using AUTO_INCREMENT for details.