How can I avoid getting this MySQL error Incorrect

Question

How can I avoid getting this MySQL error Incorrect column specifier for column topic_id ?

MySQL Error...

#1063 - Incorrect column specifier for column 'topic_id'

SQL Schema...

CREATE TABLE discussion_topics (
    topic_id char(36) NOT NULL AUTO_INCREMENT,
    project_id char(36) NOT NULL,
    topic_subject VARCHAR(255) NOT NULL,
    topic_content TEXT default NULL,
    date_created DATETIME NOT NULL,
    date_last_post DATETIME NOT NULL,
    created_by_user_id char(36) NOT NULL,
    last_post_user_id char(36) NOT NULL,
    posts_count char(36) default NULL,
    PRIMARY KEY (topic_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;

Answer 1

You cannot auto increment the char values. It should be int or long(integers or floating points). Try with this,

CREATE TABLE discussion_topics (
    topic_id int(5) NOT NULL AUTO_INCREMENT,
    project_id char(36) NOT NULL,
    topic_subject VARCHAR(255) NOT NULL,
    topic_content TEXT default NULL,
    date_created DATETIME NOT NULL,
    date_last_post DATETIME NOT NULL,
    created_by_user_id char(36) NOT NULL,
    last_post_user_id char(36) NOT NULL,
    posts_count char(36) default NULL,
    PRIMARY KEY (`topic_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;

Hope this helps

Answer 2

The auto_increment property only works for numeric columns (integer and floating point), not char columns:

CREATE TABLE discussion_topics (
    topic_id INT NOT NULL AUTO_INCREMENT,
    project_id char(36) NOT NULL,
    topic_subject VARCHAR(255) NOT NULL,
    topic_content TEXT default NULL,
    date_created DATETIME NOT NULL,
    date_last_post DATETIME NOT NULL,
    created_by_user_id char(36) NOT NULL,
    last_post_user_id char(36) NOT NULL,
    posts_count char(36) default NULL,
    PRIMARY KEY (topic_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;

Answer 3

I was having the same problem, but using Long type. I changed for INT and it worked for me.

CREATE TABLE lists (
 id INT NOT NULL AUTO_INCREMENT,
 desc varchar(30),
 owner varchar(20),
 visibility boolean,
 PRIMARY KEY (id)
 );

Answer 4

Quoting the doc:

Some attributes do not apply to all data types. AUTO_INCREMENT applies only to integer and floating-point types. DEFAULT does not apply to the BLOB or TEXT types.

In your case, you're trying to apply AUTO_INCREMENT modifier to char column. To solve this, either drop AUTO_INCREMENT altogether (that means you'll have to generate a unique id on the application level) or just change topic_id type to the relevant integer one.

As a sidenote, it makes little sense using char(36) to store the posts count, so that column's type probably has to be changed as well. It looks like you're going this way to prevent integer overflow - but if you're dealing with more than 18446744073709551615 posts (the biggest number that can be stored in BIGINT UNSIGNED column) in a single topic, you have far bigger problem on your side probably. )

Answer 5

To use AUTO_INCREMENT you need to deifne column as INT or floating-point types, not CHAR.

AUTO_INCREMENT use only unsigned value, so it's good to use UNSIGNED as well;

CREATE TABLE discussion_topics (

     topic_id INT NOT NULL unsigned AUTO_INCREMENT,
     project_id char(36) NOT NULL,
     topic_subject VARCHAR(255) NOT NULL,
     topic_content TEXT default NULL,
     date_created DATETIME NOT NULL,
     date_last_post DATETIME NOT NULL,
     created_by_user_id char(36) NOT NULL,
     last_post_user_id char(36) NOT NULL,
     posts_count char(36) default NULL,
     PRIMARY KEY (topic_id) 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;