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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.

Unique constraints & insert or update for both MySQL and SQLite

I am looking for a way to define a set of columns as unique and then insert a new entry into the table or update the row if the columns aren't unique. I have done some research and found ways to do it, but I couldn't find anything that is compatible with both MySQL and SQLite.
Say I have the following table:
CREATE TABLE `users` (
`id` INT NOT NULL AUTO_INCREMENT,
`uuid` VARCHAR ( 64 ) NOT NULL,
`name` VARCHAR ( 32 ) NOT NULL,
`date` BIGINT NULL,
PRIMARY KEY ( id )
);
I want uuid and date to be unique so that there can be multiple entries for one uuid or one date, but not for one combination of uuid and date. What I initially wanted to do is set the primary key to those:
PRIMARY KEY ( uuid, date )
However, for some reason I won't be able to use null values for date when doing this.
I have also found something about a constraint, but I am not sure if this works:
CONSTRAINT user UNIQUE ( `uuid`, `date` )
Now I want to insert a new row into this table, but update the existing row if a row with the same uuid and date already exists. I have found a few ways but they are either not doing what I want or not compatible with both MySQL and SQLite:
INSERT INTO ... ON DUPLICATE KEY doesn't work with SQLite
REPLACE INTO will delete anything I don't specify instead of updating
I have been doing research for quite a while but I couldn't find a solution that worked for me. Any help appreciated.

SQLite solution (same principle should apply in mysql)
You could simply add a UNIQUE index (at least for SQLite for which this is for) so you could have :-
DROP TABLE IF EXISTS `users`;
CREATE TABLE IF NOT EXISTS `users` (
`id` INTEGER, //<<<<<<<<<< See notes below
`uuid` VARCHAR ( 64 ) NOT NULL,
`name` VARCHAR ( 32 ) NOT NULL,
`date` BIGINT NULL,
PRIMARY KEY ( `id` )
);
CREATE UNIQUE INDEX IF NOT EXISTS uuid_date ON `users` (`uuid`,`date`); //<<<<<<<<<<
Note AUTO_INCREMENT results in a failure for SQLite as it's not a keyword, the correct keyword in SQlite is AUTOINCREMENT. However, it's been omitted as it's probably not required as INTEGER PRIMARY KEY (or the implicit by specifiying PRIMARY KEY (id)) will result in a uniqiue id being automatically generated if no value is supplied for the column when inserting.
SQLite requires INTEGER, not INT, for the automatically generated id. NOT NULL and also UNIQUE are implied so no need to specify them.
Here's two sets of example inserts each duplicating the uuid/date combination thus updating instead of inserting and also inserting with same uuid but different date and vice-versa :-
INSERT OR REPLACE INTO `users` VALUES(null,'Fred01234567','Fred Bloggs the 1st','20180101');
INSERT OR REPLACE INTO `users` VALUES(null,'Fred01234567','Fred Bloggs the 2nd','20180101'); -- <<<< DUPLICATE
INSERT OR REPLACE INTO `users` VALUES(null,'Fred99999999','Fred Bloggs the 2nd','20180101'); -- <<<< different uuid same date
INSERT OR REPLACE INTO `users` VALUES(null,'Fred01234567','Fred Bloggs the 2nd','99999999'); -- <<<< same uuid different date
INSERT OR REPLACE INTO `users` (`uuid`,'name','date') VALUES('Fred76543210','Fred NotBloggs the 1st','20180202');
INSERT OR REPLACE INTO `users` (`uuid`,'name','date') VALUES('Fred76543210','Fred NotBloggs the 1st','20180202');
INSERT OR REPLACE INTO `users` (`uuid`,'name','date') VALUES('Fred99999999','Fred NotBloggs the 1st','20180202');
INSERT OR REPLACE INTO `users` (`uuid`,'name','date') VALUES('Fred76543210','Fred NotBloggs the 1st','99999999');
SELECT * FROM `users`;
Results are :-

I have been googling for a few hours and did some testing with both MySQL and SQLite and I think I found a working solution.
To make the combination of uuid and date unique, I have added a unique constraint to the table. To insert a new row or 'update' an existing row, I am using REPLACE INTO ... SELECT.
To create the table:
CREATE TABLE IF NOT EXISTS `users` (
`id` INT NOT NULL AUTO_INCREMENT, // use INTEGER NOT NULL for SQLite
`uuid` VARCHAR ( 64 ) NOT NULL,
`name` VARCHAR ( 32 ) NOT NULL,
`date` BIGINT NULL,
CONSTRAINT `uuid_date` UNIQUE ( `uuid`, `date` ),
PRIMARY KEY ( `id` )
);
The CONSTRAINT will make sure the combination of uuid and date is always unique.
For inserting data, I use REPLACE INTO ... SELECT, where I enter all (new) values in the SELECT query and enter the column names for all columns I haven't specified a value for, to ensure it will keep their values intact rather than deleting them when the existing row is replaced.
REPLACE INTO `users`
SELECT `id`, `uuid`, ?, `date`
FROM `users` WHERE `uuid` = ? AND `date` = ?;
Of course, because in this case there are no columns that can be lost when using a normal REPLACE INTO, so I could also use:
REPLACE INTO `users` ( `uuid`, `name`, `date` ) VALUES ( ?, ?, ? );
However, the REPLACE INTO ... SELECT query can be useful when I have a table with more columns and there are actually columns that can be lost when not selecting them.

Sorry about all the comments. Here is how I achieved what I think you are going for. You are going to lose the id as Primary Key on your users table. You will also have to stage your insert variables in a table. But you will get your end results. Sorry I do not have a better solution.
DROP TABLE users;
DROP TABLE users2;
CREATE TABLE `users` (
`uuid` VARCHAR ( 64 ) NOT NULL,
`name` VARCHAR ( 32 ) NOT NULL,
`date` BIGINT NULL
);
ALTER TABLE `users` ADD PRIMARY KEY(`uuid`,`date`);
INSERT INTO users (`name`,`uuid`,`date`) SELECT '','123','2018-04-01';
CREATE TABLE `users2` (
`uuid` VARCHAR ( 64 ) NOT NULL,
`name` VARCHAR ( 32 ) NOT NULL,
`date` BIGINT NULL
);
INSERT INTO users2 (`name`,`uuid`,`date`) SELECT 'brad','123','2018-04-01';
REPLACE INTO users SELECT `uuid`,`name`,`date` FROM users2 GROUP BY `uuid`,`date`;
SELECT * FROM users;`

Need to improve performance query a table with millions of rows - SQL Server

This query on an audit trail table starts slowing down once the load increases in performance testing (reads and inserts) and I've done what I can with indexing. With this query and these tables and indexes, what more can I do?
CREATE TABLE [dbo].[mod2] (
[id] [int] IDENTITY,
[userId] [int] NOT NULL,
[epochTime] [bigint] NOT NULL,
[forecastId] [int] NOT NULL,
[description] [char](12) NOT NULL,
[auxText] [text] NULL,
[auxDate] [date] NULL
);
ALTER TABLE [dbo].[mod2] ADD CONSTRAINT PK_mod2 PRIMARY KEY(ID);
ALTER TABLE [dbo].[mod2] WITH CHECK
ADD CONSTRAINT [FK_mod2_forecastId] FOREIGN KEY([forecastId])
REFERENCES [dbo].[forecast] ([id]);
ALTER TABLE [dbo].[mod2] CHECK CONSTRAINT [FK_mod2_forecastId];
ALTER TABLE [dbo].[mod2] WITH CHECK
ADD CONSTRAINT [FK_mod2_userId] FOREIGN KEY([userId])
REFERENCES [dbo].[user] ([id]);
ALTER TABLE [dbo].[mod2] CHECK CONSTRAINT [FK_mod2_userId];
CREATE NONCLUSTERED INDEX IX_modification_auxDate ON [dbo].[mod2] (auxDate ASC);
CREATE NONCLUSTERED INDEX IX_modification_epochTime ON [dbo].[mod2] (epochTime ASC);
CREATE NONCLUSTERED INDEX IX_modification_description ON [dbo].[mod2] (description ASC);
CREATE NONCLUSTERED INDEX IX_modification_forecastId ON [dbo].[mod2] (forecastId ASC);
CREATE NONCLUSTERED INDEX IX_modification_userId ON [dbo].[mod2] (userId ASC);
and this is my query:
SELECT name, epochTime, auxDate
FROM mod2 WITH (NOLOCK)
JOIN [user] ON [user].id = mod2.userId
WHERE forecastId = ? AND description = ? AND auxDate = ?
This is a legacy system and it was crawling before I put these indexes on it and changed the description field from VARCHAR to CHAR
The forecast and user id fields are INT and indexed similarly.

There are a few things you can do here.
One is to ensure there is a clustered index on user for its id field (probably there is, but making sure won't hurt).
The individual indexes you put in are not great - in particular given the query pattern you have shown - either non of them would be used (as they do not contain the full data), or some of them might be used and then the full table will be refered to in order to pick out the remaining data required to fulfill the query.
For this particular query, for mod2, I'd likely add an index on userId with it covering forecastId, description and auxDate - this way the index contains all the data required to fulfil the query (on the mod2 side).

CREATE NONCLUSTERED INDEX IXmod2_user_desc_forecast_auxdate
ON [dbo].[mod2] (userId, forecastId, description, auxDate DESC);
and the query plans looks like this:
|--Nested Loops(Inner Join, OUTER REFERENCES:([MyDB].[dbo].[mod2].[id]) OPTIMIZED)
|--Nested Loops(Inner Join, OUTER REFERENCES:([MyDB].[dbo].[user].[id], [Expr1006]) WITH UNORDERED PREFETCH)
| |--Clustered Index Scan(OBJECT:([MyDB].[dbo].[user]. [PK_user]), ORDERED FORWARD)
| |--Index Seek(OBJECT:([MyDB].[dbo].[mod2].[IX_mod2_user_desc_forecast_auxdate]), SEEK:([MyDB].[dbo].[mod2].[userId]=[MyDB].[dbo].[user].[id] AND [MyDB].[dbo].[mod2].[forecastId]=(40357) AND [MyDB].[dbo].[mod2].[description]='SAVE' AND [MyDB].[dbo].[mod2].[auxDate]='2017-01-31') ORDERED FORWARD)
|--Clustered Index Seek(OBJECT:([MyDB].[dbo].[mod2].[PK_mod2]), SEEK:([MyDB].[dbo].[mod2].[id]=[MyDB].[dbo].[mod2].[id]) LOOKUP ORDERED FORWARD)

How to add an auto increment column in java?

I want to add the database from my jform and there's a column which will be auto incremented, like when i click done, the data will be inserted and a column receipt_no will have a value 1. Next time I click done then this value should be 2 and so on.
So the problem is, i have created a table with receipt_no as the primary key and auto increment, so what should be my query in java, to add the data correctly in the table.
String sql = "insert into table_name values('"++"',...)";
Can you help me in this query?

Step 1: Creating table in MySQL
CREATE TABLE `user_master` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`Firstname` varchar(45) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Step 2: Insert record
INSERT INTO user_master (`Firstname`) values('Vicky');
Step 3: Fetch record
SELECT * FROM user_master;

I can't comment so there is an answer to the comment you posted in your question:
If your table is
CREATE TABLE users(
id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
firstname VARCHAR(25) NOT NULL,
lastname VARCHAR(25) NOT NULL,
);
You can simply auto_increment the primary by not giving it on your SQL request:
INSERT INTO users(firstname, lastname) VALUES('Steve', 'Jobs');
Java don't have to generate auto increment, it is SQL job :)

How to programmatically transfer a lot of data between tables?

i have two tables where in the first one i have 14 millions and in the second one i have 1.5 million of data.
So i wonder how could i transfer this data to another table to be normalized ?
And how do i convert some type to another, for example: i have a field called 'year' but its type is varchar, but i want it an integer instead, how do i do that ?
I thought about do this using JDBC in a loop while from java, but i think this is not effeciently.
// 1.5 million of data
CREATE TABLE dbo.directorsmovies
(
movieid INT NULL,
directorid INT NULL,
dname VARCHAR (500) NULL,
addition VARCHAR (1000) NULL
)
//14 million of data
CREATE TABLE dbo.movies
(
movieid VARCHAR (20) NULL,
title VARCHAR (400) NULL,
mvyear VARCHAR (100) NULL,
actorid VARCHAR (20) NULL,
actorname VARCHAR (250) NULL,
sex CHAR (1) NULL,
as_character VARCHAR (1500) NULL,
languages VARCHAR (1500) NULL,
genres VARCHAR (100) NULL
)
And this is my new tables:
DROP TABLE actor
CREATE TABLE actor (
id INT PRIMARY KEY IDENTITY,
name VARCHAR(200) NOT NULL,
sex VARCHAR(1) NOT NULL
)
DROP TABLE actor_character
CREATE TABLE actor_character(
id INT PRIMARY KEY IDENTITY,
character VARCHAR(100)
)
DROP TABLE director
CREATE TABLE director(
id INT PRIMARY KEY IDENTITY,
name VARCHAR(200) NOT NULL,
addition VARCHAR(150)
)
DROP TABLE movie
CREATE TABLE movie(
id INT PRIMARY KEY IDENTITY,
title VARCHAR(200) NOT NULL,
year INT
)
DROP TABLE language
CREATE TABLE language(
id INT PRIMARY KEY IDENTITY,
language VARCHAR (100) NOT NULL
)
DROP TABLE genre
CREATE TABLE genre(
id INT PRIMARY KEY IDENTITY,
genre VARCHAR(100) NOT NULL
)
DROP TABLE director_movie
CREATE TABLE director_movie(
idDirector INT,
idMovie INT,
CONSTRAINT fk_director_movie_1 FOREIGN KEY (idDirector) REFERENCES director(id),
CONSTRAINT fk_director_movie_2 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT pk_director_movie PRIMARY KEY(idDirector,idMovie)
)
DROP TABLE genre_movie
CREATE TABLE genre_movie(
idGenre INT,
idMovie INT,
CONSTRAINT fk_genre_movie_1 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT fk_genre_movie_2 FOREIGN KEY (idGenre) REFERENCES genre(id),
CONSTRAINT pk_genre_movie PRIMARY KEY (idMovie, idGenre)
)
DROP TABLE language_movie
CREATE TABLE language_movie(
idLanguage INT,
idMovie INT,
CONSTRAINT fk_language_movie_1 FOREIGN KEY (idLanguage) REFERENCES language(id),
CONSTRAINT fk_language_movie_2 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT pk_language_movie PRIMARY KEY (idLanguage, idMovie)
)
DROP TABLE movie_actor
CREATE TABLE movie_actor(
idMovie INT,
idActor INT,
CONSTRAINT fk_movie_actor_1 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT fk_movie_actor_2 FOREIGN KEY (idActor) REFERENCES actor(id),
CONSTRAINT pk_movie_actor PRIMARY KEY (idMovie,idActor)
)
UPDATE:
I'm using SQL Server 2008.
Sorry guys i forgot to mention that are different databases :
The not normalized is call disciplinedb and the my normalized call imdb.
Best regards,
Valter Henrique.

If both tables are in the same database, then the most efficient transfer is to do it all within the database, preferably by sending a SQL statement to be executed there.
Any movement of data from the d/b server to somewhere else and then back to the d/b server is to be avoided unless there is a reason it can only be transformed off-server. If the destination is different server, then this is much less of an issue.

Though my tables were dwarfs compared to yours, I got over this kind of problem once with stored procedures. For MySQL, below is a simplified (and untested) essence of my script, but something similar should work with all major SQL bases.
First you should just add a new integer year column (int_year in example) and then iterate over all rows using the procedure below:
DROP PROCEDURE IF EXISTS move_data;
CREATE PROCEDURE move_data()
BEGIN
DECLARE done INT DEFAULT 0;
DECLARE orig_id INT DEFAULT 0;
DECLARE orig_year VARCHAR DEFAULT "";
DECLARE cur1 CURSOR FOR SELECT id, year FROM table1;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
PREPARE stmt FROM "UPDATE table1 SET int_year = ? WHERE id = ?";
read_loop: LOOP
FETCH cur1 INTO orig_id, orig_year;
IF done THEN
LEAVE read_loop;
END IF;
SET #year= orig_year;
SET #id = orig_id;
EXECUTE stmt USING #orig_year, #id;
END LOOP;
CLOSE cur1;
END;
And to start the procedure, just CALL move_data().
The above SQL has two major ideas to speed it up:
Use CURSORS to iterate over a large table
Use PREPARED statement to quickly execute pre-known commands
PS. for my case this speeded things up from ages to seconds, though in your case it can still take a considerable amount of time. So it would be probably best to execute from command line, not some web interface (e.g. PhpMyAdmin).

I just recently did this for ~150 Gb of data. I used a pair of merge statements for each table. The first merge statement said "if it's not in the destination table, copy it there" and the second said "if it's in the destination table, delete it from the source". I put both in a while loop and only did 10000 rows in each operation at a time. Keeping it on the server (and not transferring it through a client) is going to be a huge boon for performance. Give it a shot!