[mysql] Insert auto increment primary key to existing table

I am trying to alter a table which has no primary key nor auto_increment column. I know how to add an primary key column but I was wondering if it's possible to insert data into the primary key column automatically (I already have 500 rows in DB and want to give them id but I don't want to do it manually). Any thoughts? Thanks a lot.

suppose you don't have column for auto increment like id, no, then you can add using following query:

ALTER TABLE table_name ADD id int NOT NULL AUTO_INCREMENT primary key FIRST

If you've column, then alter to auto increment using following query:

 ALTER TABLE table_name MODIFY column_name datatype(length) AUTO_INCREMENT PRIMARY KEY

yes, something like this would do it, might not be the best though, you might wanna make a backup

$get_query = mysql_query("SELECT `any_field` FROM `your_table`");

$auto_increment_id = 1;

while($row = mysql_fetch_assoc($get_query))
{
  $update_query = mysql_query("UPDATE `your_table` SET `auto_increment_id`=$auto_increment_id WHERE `any_field` = '".$row['any_field']."'");
  $auto_increment_id++;
}

notice that the the any_field you select must be the same when updating.

ALTER TABLE tableName MODIFY tableNameID MEDIUMINT NOT NULL AUTO_INCREMENT;

Here tableName is name of your table,

tableName is your column name which is primary has to be modified

MEDIUMINT is a data type of your existing primary key

AUTO_INCREMENT you have to add just auto_increment after not null

It will make that primary key auto_increment......

Hope this is helpful:)

You can add a new Primary Key column to an existing table, which can have sequence numbers, using command:

ALTER TABLE mydb.mytable ADD pk_columnName INT IDENTITY 

For those like myself getting a Multiple primary key defined error try:

ALTER TABLE `myTable` ADD COLUMN `id` INT AUTO_INCREMENT UNIQUE FIRST NOT NULL;

On MySQL v5.5.31 this set the id column as the primary key for me and populated each row with an incrementing value.

I was able to adapt these instructions take a table with an existing non-increment primary key, and add an incrementing primary key to the table and create a new composite primary key with both the old and new keys as a composite primary key using the following code:

DROP TABLE  IF EXISTS SAKAI_USER_ID_MAP;

CREATE TABLE SAKAI_USER_ID_MAP (
       USER_ID             VARCHAR (99) NOT NULL,
       EID                 VARCHAR (255) NOT NULL,
       PRIMARY KEY (USER_ID)
);

INSERT INTO SAKAI_USER_ID_MAP VALUES ('admin', 'admin');
INSERT INTO SAKAI_USER_ID_MAP VALUES ('postmaster', 'postmaster');

ALTER TABLE  SAKAI_USER_ID_MAP 
  DROP PRIMARY KEY, 
  ADD _USER_ID INT AUTO_INCREMENT NOT NULL FIRST, 
  ADD PRIMARY KEY ( _USER_ID, USER_ID );

When this is done, the _USER_ID field exists and has all number values for the primary key exactly as you would expect. With the "DROP TABLE" at the top, you can run this over and over to experiment with variations.

What I have not been able to get working is the situation where there are incoming FOREIGN KEYs that already point at the USER_ID field. I get this message when I try to do a more complex example with an incoming foreign key from another table.

#1025 - Error on rename of './zap/#sql-da07_6d' to './zap/SAKAI_USER_ID_MAP' (errno: 150)

I am guessing that I need to tear down all foreign keys before doing the ALTER table and then rebuild them afterwards. But for now I wanted to share this solution to a more challenging version of the original question in case others ran into this situation.

How to write PHP to ALTER the already existing field (name, in this example) to make it a primary key? W/o, of course, adding any additional 'id' fields to the table..

This a table currently created - Number of Records found: 4 name VARCHAR(20) YES breed VARCHAR(30) YES color VARCHAR(20) YES weight SMALLINT(7) YES

This an end result sought (TABLE DESCRIPTION) -

Number of records found: 4 name VARCHAR(20) NO PRI breed VARCHAR(30) YES color VARCHAR(20) YES weight SMALLINT(7) YES

Instead of getting this -

Number of Records found: 5 id int(11) NO PRI name VARCHAR(20) YES breed VARCHAR(30) YES color VARCHAR(20) YES weight SMALLINT(7) YES

after trying..

$query = "ALTER TABLE racehorses ADD id INT NOT NULL AUTO_INCREMENT FIRST, ADD PRIMARY KEY (id)";

how to get this? -

Number of records found: 4 name VARCHAR(20) NO PRI breed VARCHAR(30) YES color VARCHAR(20) YES weight SMALLINT(7) YES

i.e. INSERT/ADD.. etc. the primary key INTO the first field record (w/o adding an additional 'id' field, as stated earlier.

The easiest and quickest I find is this

ALTER TABLE mydb.mytable 
ADD COLUMN mycolumnname INT NOT NULL AUTO_INCREMENT AFTER updated,
ADD UNIQUE INDEX mycolumnname_UNIQUE (mycolumname ASC);

I was facing the same problem so what I did I dropped the field for the primary key then I recreated it and made sure that it is auto incremental . That worked for me . I hope it helps others

In order to make the existing primary key as auto_increment, you may use:

ALTER TABLE table_name MODIFY id INT AUTO_INCREMENT;

Well, you have multiple ways to do this: -if you don't have any data on your table, just drop it and create it again.

Dropping the existing field and creating it again like this

ALTER TABLE test DROP PRIMARY KEY, DROP test_id, ADD test_id int AUTO_INCREMENT NOT NULL FIRST, ADD PRIMARY KEY (test_id);

Or just modify it

ALTER TABLE test MODIFY test_id INT AUTO_INCREMENT NOT NULL, ADD PRIMARY KEY (test_id);

Export your table, then empty your table, then add field as unique INT, then change it to AUTO_INCREMENT, then import your table again that you exported previously.