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Transform composite primary key into ID [duplicate]

I have a pre-existing table, containing 'fname', 'lname', 'email', 'password' and 'ip'. But now I want an auto-increment column. However, when I enter:
ALTER TABLE users
ADD id int NOT NULL AUTO_INCREMENT
I get the following:
#1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key
Any advice?:)

Try this
ALTER TABLE `users` ADD `id` INT NOT NULL AUTO_INCREMENT;
for an existing primary key

If you don't care whether the auto-id is used as PRIMARY KEY, you can just do
ALTER TABLE `myTable` ADD COLUMN `id` INT AUTO_INCREMENT UNIQUE FIRST;
I just did this and it worked a treat.

If you want to add AUTO_INCREMENT in an existing table, need to run following SQL command:
ALTER TABLE users ADD id int NOT NULL AUTO_INCREMENT primary key

First you have to remove the primary key of the table
ALTER TABLE nametable DROP PRIMARY KEY
and now yo can add the autoincrement ...
ALTER TABLE nametable ADD id INT NOT NULL AUTO_INCREMENT PRIMARY KEY

Well, you must first drop the auto_increment and primary key you have and then add yours, as follows:
-- drop auto_increment capability
alter table `users` modify column id INT NOT NULL;
-- in one line, drop primary key and rebuild one
alter table `users` drop primary key, add primary key(id);
-- re add the auto_increment capability, last value is remembered
alter table `users` modify column id INT NOT NULL AUTO_INCREMENT;

If you run the following command :
ALTER TABLE users ADD id int NOT NULL AUTO_INCREMENT PRIMARY KEY;
This will show you the error :
ERROR 1060 (42S21): Duplicate column name 'id'
This is because this command will try to add the new column named id to the existing table.
To modify the existing column you have to use the following command :
ALTER TABLE users MODIFY id int NOT NULL AUTO_INCREMENT PRIMARY KEY;
This should work for changing the existing column constraint....!

Delete the primary key of a table if it exists:
ALTER TABLE `tableName` DROP PRIMARY KEY;
Adding an auto-increment column to a table :
ALTER TABLE `tableName` ADD `Column_name` INT PRIMARY KEY AUTO_INCREMENT;
Modify the column which we want to consider as the primary key:
alter table `tableName` modify column `Column_name` INT NOT NULL AUTO_INCREMENT PRIMARY KEY;

Just change the ADD to MODIFY and it will works !
Replace
ALTER TABLE users ADD id int NOT NULL AUTO_INCREMENT
To
ALTER TABLE users MODIFY id int NOT NULL AUTO_INCREMENT;

Drop the primary index from the table:
ALTER TABLE `tableName` DROP INDEX `PRIMARY`;
Then add the id column (without a primary index). I have used a big int because I am going to have lots of data but INT(11) should work just as well:
ALTER TABLE `tableName` ADD COLUMN `id` BIGINT(11) NOT NULL FIRST;
Then modify the column with auto-increment (thanks php). It needs to be a primary key:
ALTER TABLE `tableName ` MODIFY COLUMN `id` BIGINT(11) UNSIGNED PRIMARY KEY AUTO_INCREMENT;
I have just tried this on a table of mine and it appears to have worked.

ALTER TABLE users CHANGE id int( 30 ) NOT NULL AUTO_INCREMENT
the integer parameter is based on my default sql setting
have a nice day

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

For PostgreSQL you have to use SERIAL instead of auto_increment.
ALTER TABLE your_table_name ADD COLUMN id SERIAL NOT NULL PRIMARY KEY

ALTER TABLE `table` ADD `id` INT NOT NULL AUTO_INCREMENT unique
Try this. No need to drop your primary key.

This SQL request works for me :
ALTER TABLE users
CHANGE COLUMN `id` `id` INT(11) NOT NULL AUTO_INCREMENT ;

If you want to add an id with a primary key and identity:
ALTER TABLE user ADD id INT NOT NULL AUTO_INCREMENT FIRST , ADD PRIMARY KEY (id);

Check for already existing primary key with different column. If yes, drop the primary key using:
ALTER TABLE Table1
DROP CONSTRAINT PK_Table1_Col1
GO
and then write your query as it is.

Proceed like that :
Make a dump of your database first
Remove the primary key like that
ALTER TABLE yourtable DROP PRIMARY KEY
Add the new column like that
ALTER TABLE yourtable add column Id INT NOT NULL AUTO_INCREMENT FIRST, ADD primary KEY Id(Id)
The table will be looked and the AutoInc updated.

ALTER TABLE CREATE CONSTRAINT IF NOT EXIST possible?

I have an application which starts (AppStarter) a web server with a web application. The Web Application has migration scripts (flyway).
I want to write some data from AppStarter through JDBC in a table. But I want to create the table if it does not exist. The table also has some constraints.
Within the AppStarter I execute following command:
CREATE CACHED TABLE PUBLIC.CORE_USERROLE_TO_PARAMETER (
ID VARCHAR(32) PRIMARY KEY NOT NULL,
VERSION INTEGER,
USER_ID VARCHAR(32)NOT NULL,
ROLE_ID VARCHAR(32) NOT NULL,
PARAMETER VARCHAR(255) NOT NULL
);
ALTER TABLE PUBLIC.CORE_USERROLE_TO_PARAMETER ADD CONSTRAINT PUBLIC.CURTBP_USER_ID FOREIGN KEY(USER_ID) REFERENCES PUBLIC.CORE_USER(ID) NOCHECK;
ALTER TABLE PUBLIC.CORE_USERROLE_TO_PARAMETER ADD CONSTRAINT PUBLIC.CURTBP_ROLE_ID FOREIGN KEY(ROLE_ID) REFERENCES PUBLIC.CORE_USER_ROLE(ID) NOCHECK;
The web app also reads some information from this table and creates the tables.
Now I have a sql migration script
CREATE CACHED TABLE IF NOT EXISTS PUBLIC.CORE_USERROLE_TO_PARAMETER (
ID VARCHAR(32) PRIMARY KEY NOT NULL,
VERSION INTEGER,
USER_ID VARCHAR(32)NOT NULL,
ROLE_ID VARCHAR(32) NOT NULL,
PARAMETER VARCHAR(255) NOT NULL
);
But how do I create the constraint only if they does not already exist?
Thanks in advance
Currently I can get if the constraints exists with
select * from INFORMATION_SCHEMA.CONSTRAINTS WHERE CONSTRAINT_NAME='CURTRP_USER_ID'
but how do I build this into a if query with H2
Edit:
I could move the constraint part in total to the migration script, but this seems somehow wrong.
I am working with H2 Database.

Following my comment, this should be possible:
ALTER TABLE PUBLIC.CORE_USERROLE_TO_PARAMETER
ADD CONSTRAINT IF NOT EXISTS PUBLIC.CURTBP_USER_ID
FOREIGN KEY(USER_ID) REFERENCES PUBLIC.CORE_USER(ID) NOCHECK;
ALTER TABLE PUBLIC.CORE_USERROLE_TO_PARAMETER
ADD CONSTRAINT IF NOT EXISTS PUBLIC.CURTBP_ROLE_ID
FOREIGN KEY(ROLE_ID) REFERENCES PUBLIC.CORE_USER_ROLE(ID) NOCHECK;

Use this query to get the foreign key constraints
SELECT * FROM INFORMATION_SCHEMA.CONSTRAINTS WHERE CONSTRAINT_TYPE = 'REFERENTIAL'

You can try ALTER TABLE IF EXISTS like CREATE IF EXISTS. If its a responsibility of your application only, and not handled by another app or script.

JDBC generated key from insert on duplicate

If you have an insert with an ON DUPLICATE KEY clause, and there is a duplicate key, is there any way to get back the primary key that was duplicated? or do I have to do my own manual query? As far as I can tell getGeneratedKeys() from the CallableStatement class will not return as a new insert wasn't actually done.
EDIT
Sorry if it wasn't clear but I want to get the PRIMARY KEY of the record back.
So if I were have the following table (excuse syntax, just typing it freehand):
CREATE TABLE some_table(
id int(11) unsigned NOT NULL AUTO_INCREMENT,
value varchar(500)NOT NULL,
count int(10) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (id),
UNIQUE KEY (value)
);
INSERT INTO some_table(value) ON DUPLICATE KEY UPDATE count = count + 1;
If I were to add 'test' as the value, a new record would be added and the id would be returned by getGeneratedKeys();
If I were to attempt to add 'test' again, the key already exists and therefore the count would be updated. What I want is the primary key/id of that row which was updated. Do I have to see that I get no results back from getGeneratedKeys() - as none where generated - and do another select after the fact?

ON DUPLICATE KEY UPDATE count = count + 1, id = LAST_INSERT_ID(id)
Note: This shouldn't be necessary as of MySQL 5.5.

H2 sql how to set column to auto_increment

i am trying to set my ID to auto_increment, but it is not doing it. i saved 2 more data into db, all are still getting 0 id. as a result i am not able to set ID as primary key.
how is it possible? can i set the field to auto_increment with JPA annotation or so?
i even tried this command which is the first attempt:
alter table user alter column id int not null auto_increment;
no affect.
can someone help me please
thanks in advance!

If you just want to set ID as a primary key which is auto generated,then sql uniqueidentifier for it.
CREATE TABLE userTable(userId uniqueidentifier primary key, userName nvarchar(50))
--create a table having userId as a primary key
INSERT INTO userTable(userId, userName ) VALUES (NEWID(), 'mohit');
INSERT INTO userTable(userId, userName ) VALUES (NEWID(), 'doniyor');
SELECT * FROM userTable
Result will be:
userId userName
{E8E0A79D-436F-49CB-BCEC-EC9E5D69F1BB} mohit
{21081DFA-7DBB-46AF-A160-550631160C25} doniyor

My Insert Into Statement is not working

I was working with UIs where the user will click the add button to add employees, but when I do it, it gives me an error like this
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`finalpayroll`.`personal_info`, CONSTRAINT `personal_info_ibfk_1`
How would I fix this?? I know I am using a parent key, and its foreign key is the User, and also take note that the parent key has already a data, but it seems my query won't work, why is that? I am using a foreign key with delete cascade and on update cascade so that when I delete a data, all of the child table rows will be deleted, vice versa. here's my key for adding or inserting statements
public void addEmployee(Personal p ,Contact c,Employee e) {
Connection conn = Jdbc.dbConn();
Statement statement = null;
String insert1 = "INSERT INTO personal_info (`First_Name`, `Middle_Initial`, `Last_Name`, `Date_Of_Birth`, `Marital_Status`, `Beneficiaries`) VALUES ('"+p.getFirstName()+"', '"+p.getMiddleInitial()+"'" +
" , '"+p.getLastName()+"', '"+p.getDateOfBirth()+"', '"+p.getMaritalStatus()+"', '"+p.getBeneficiaries()+"')";
try {
statement = conn.createStatement();
statement.executeUpdate(insert1);
statement.close();
conn.close();
JOptionPane.showMessageDialog(null, "Employee Added!!");
} catch(Exception ex) {
ex.printStackTrace();
}
}
Users table:
CREATE TABLE `users` (
`idusers` int(11) NOT NULL AUTO_INCREMENT,
`emp_id` varchar(45) DEFAULT NULL,
`emp_pass` varchar(45) DEFAULT NULL,
PRIMARY KEY (`idusers`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1
Personal_info table:
CREATE TABLE `personal_info` (
`idpersonal_info` int(11) NOT NULL AUTO_INCREMENT,
`First_Name` varchar(45) DEFAULT NULL,
`Middle_Initial` varchar(45) DEFAULT NULL,
`Last_Name` varchar(45) DEFAULT NULL,
`Date_Of_Birth` varchar(45) DEFAULT NULL,
`Marital_Status` varchar(45) DEFAULT NULL,
`Beneficiaries` varchar(45) DEFAULT NULL,
PRIMARY KEY (`idpersonal_info`),
CONSTRAINT `personal_info_ibfk_1`
FOREIGN KEY (`idpersonal_info`)
REFERENCES `users` (`idusers`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1

You are trying to insert a record with 6 fields: First_Name, Middle_Initial, Last_Name, Date_Of_Birth, Marital_Status and Beneficiaries. Your schema is currently unknown but none of these fields seem to be a candidate foreign key to id of User table you mentioned. Thus I think there is a default value for that foreign key column and that default value is missing in User table.
Needless to say, you shouldn't have a default value for a foreign key of any table..
I am adding these information regarding your questions in comments and update on your question:
A foreign key is a link between a child table and parent table, personal_info and users tables in your case respectively. Child table's foreign key column must reference to a key value in parent table which means that for every value in child table's FK column, there must be a value in parent table's linked column.
Now, in your case when you try to insert a new personal_info record MySQL assigns a idpersonal_info to it, since you defined it as auto increment. But since there is a link to users table, MySQL searchs for the new idpersonal_info to be inserted in users table's idusers column. And as you are getting this exception, you surely don't have that value in the users table.
You can change your table structure as follows:
CREATE TABLE `personal_info` (
`idpersonal_info` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11) NOT NULL,
... OTHER FIELD DEFINITIONS,
PRIMARY KEY (`idpersonal_info`),
CONSTRAINT `user_id_fk_1` FOREIGN KEY (`user_id`) REFERENCES `users` (`idusers`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB
And your query will need to include user_id field as well. So it will be something like this:
INSERT INTO personal_info
(`user_id`, `First_Name`, `Middle_Initial`, `Last_Name`, `Date_Of_Birth`, `Marital_Status`, `Beneficiaries`)
VALUES ( .... SET YOUR VALUES HERE. DON'T FORGET TO SET A VALID USER_ID

Looks like in your Personal_Info table you have a column called "finalpayroll", that points to a column in another table (a foreign key) and it's required (not nullable). In your insert you're not giving it a value. So what you could do is make that column nullable.
Or could be the other way around as #Konstantin Naryshkin is saying

What the error means is that you are trying to insert a value into a column with a foreign key a value that is not in the remote table.
I assume that there is a user column that we are not seeing. Since you are not explicitly setting the value, I assume that it is getting a default. The default value is not in the parent table.