How to add a primary key to a MySQL table? - mysql

Question

This is what I tried but it fails:
alter table goods add column `id` int(10) unsigned primary AUTO_INCREMENT;
Does anyone have a tip?

Answer 1

After adding the column, you can always add the primary key:
ALTER TABLE goods ADD PRIMARY KEY(id)
As to why your script wasn't working, you need to specify PRIMARY KEY, not just the word PRIMARY:
alter table goods add column `id` int(10) unsigned primary KEY AUTO_INCREMENT;

Answer 2

Existing Column
If you want to add a primary key constraint to an existing column all of the previously listed syntax will fail.
To add a primary key constraint to an existing column use the form:
ALTER TABLE `goods`
MODIFY COLUMN `id` INT(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT;

Answer 3

If your table is quite big better not use the statement:
alter table goods add column `id` int(10) unsigned primary KEY AUTO_INCREMENT;
because it makes a copy of all data in a temporary table, alter table and then copies it back.
Better do it manually.
Rename your table:
rename table goods to goods_old;
create new table with primary key and all necessary indexes:
create table goods (
id int(10) unsigned not null AUTO_INCREMENT
... other columns ...
primary key (id)
);
move all data from the old table into new, disabling keys and indexes to speed up copying:
-- USE THIS FOR MyISAM TABLES:
SET UNIQUE_CHECKS=0;
ALTER TABLE goods DISABLE KEYS;
INSERT INTO goods (... your column names ...) SELECT ... your column names FROM goods_old;
ALTER TABLE goods ENABLE KEYS;
SET UNIQUE_CHECKS=1;
OR
-- USE THIS FOR InnoDB TABLES:
SET AUTOCOMMIT = 0; SET UNIQUE_CHECKS=0; SET FOREIGN_KEY_CHECKS=0;
INSERT INTO goods (... your column names ...) SELECT ... your column names FROM goods_old;
SET FOREIGN_KEY_CHECKS=1; SET UNIQUE_CHECKS=1; COMMIT; SET AUTOCOMMIT = 1;
It takes 2 000 seconds to add PK to a table with ~200 mln rows.

Answer 4

Not sure if this matters to anyone else, but I prefer the id for the table to be the first column in the database. The syntax for that is:
ALTER TABLE your_db.your_table ADD COLUMN `id` int(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT FIRST;
Which is just a slight improvement over the first answer. If you wanted it to be in a different position, then
ALTER TABLE unique_address ADD COLUMN `id` int(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT AFTER some_other_column;
HTH,
-ft

Answer 5

Use this query,
alter table `table_name` add primary key(`column_name`);

Answer 6

This code work in my mysql db:
ALTER TABLE `goods`
ADD COLUMN `id` INT NOT NULL AUTO_INCREMENT,
ADD PRIMARY KEY (`id`);

Answer 7

For me, none of suggestions worked giving me the errors of syntax, so I just gave a try using phpmyadmin(version 4.9.2), (10.4.10-MariaDB) and added id column with auto-increment primary key. Id column was nicely added from the first element.
Query output was:
ALTER TABLE table_name ADD id INT NOT NULL AUTO_INCREMENT FIRST, ADD PRIMARY KEY (id);

Answer 8

ALTER TABLE GOODS MODIFY ID INT(10) NOT NULL PRIMARY KEY;

Answer 9

Try this,
alter table goods add column `id` int(10) unsigned primary key auto_increment

Answer 10

ALTER TABLE `goods`
MODIFY COLUMN `id` INT(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT;

Answer 11

If previously you already have one or more primary keys and you want to include more column as primary key, you need to add DROP PRIMARY KEY in your statement and re-mention previous keys along with new ones in ADD PRIMARY KEY section. Take a look at the following example..
Previously, my_test_table had only a single primary key column named old_key. Then we add a new column named new_key.
ALTER TABLE my_test_table ADD COLUMN new_key INT; -- Or whatever data type you need
If we want to make our table to have primary key set {old_key, new_key}, then the following statement can be used:
ALTER TABLE my_test_table
DROP PRIMARY KEY, -- You have to add this
ADD PRIMARY KEY(
old_key, -- Re-mention the old key
new_key -- And mention also the new one
);

Answer 12

Remove quotes to work properly...
alter table goods add column id int(10) unsigned primary KEY AUTO_INCREMENT;