How to add AUTO_INCREMENT to an existing column?

问题

How do I add auto_increment to an existing column of a MySQL table?

回答1:

I think you want to MODIFY the column as described for the ALTER TABLE command. It might be something like this:

ALTER TABLE users MODIFY id INTEGER NOT NULL AUTO_INCREMENT;

Before running above ensure that id column has a Primary index.

回答2:

Method to add AUTO_INCREMENT to a table with data while avoiding “Duplicate entry” error:

Make a copy of the table with the data using INSERT SELECT:

CREATE TABLE backupTable LIKE originalTable; 
INSERT backupTable SELECT * FROM originalTable;

Delete data from originalTable (to remove duplicate entries):
```
TRUNCATE TABLE originalTable;
```

To add AUTO_INCREMENT and PRIMARY KEY

ALTER TABLE originalTable ADD id INT PRIMARY KEY AUTO_INCREMENT;

Copy data back to originalTable (do not include the newly created column (id), since it will be automatically populated)
```
INSERT originalTable (col1, col2, col3) 
SELECT col1, col2,col3
FROM backupTable;
```
Delete backupTable:
```
DROP TABLE backupTable;
```

I hope this is useful!

More on the duplication of tables using CREATE LIKE:

Duplicating a MySQL table, indexes and data

回答3:

Alter table table_name modify column_name datatype(length) AUTO_INCREMENT PRIMARY KEY

You should add primary key to auto increment, otherwise you got error in mysql.

回答4:

Simply just add auto_increment Constraint In column or MODIFY COLUMN :-

 ALTER TABLE `emp` MODIFY COLUMN `id` INT NOT NULL UNIQUE AUTO_INCREMENT FIRST;

Or add a column first then change column as -

1. Alter TABLE `emp` ADD COLUMN `id`;

2. ALTER TABLE `emp` CHANGE COLUMN `id` `Emp_id` INT NOT NULL UNIQUE AUTO_INCREMENT FIRST;

回答5:

This worked for me in case you want to change the AUTO_INCREMENT-attribute for a not-empty-table:

1.)Exported the whole table as .sql file
2.)Deleted the table after export
2.)Did needed change in CREATE_TABLE command
3.)Executed the CREATE_TABLE and INSERT_INTO commands from the .sql-file
...et viola

回答6:

I managed to do this with the following code:

ALTER TABLE `table_name`
CHANGE COLUMN `colum_name` `colum_name` INT(11) NOT NULL AUTO_INCREMENT FIRST;

This is the only way I could make a column auto increment.

INT(11) shows that the maximum int length is 11, you can skip it if you want.

回答7:

Alter table table_name modify table_name.column_name data_type AUTO_INCREMENT;

eg:

Alter table avion modify avion.av int AUTO_INCREMENT;

回答8:

ALTER TABLE Table name ADD column datatype AUTO_INCREMENT,ADD primary key(column);

来源：https://stackoverflow.com/questions/5035836/how-to-add-auto-increment-to-an-existing-column

标签

mysql

auto-increment