How to add AUTO_INCREMENT to an existing table [duplicate] - mysql

I would like to change the column type to AUTO_INCREMENT within an existing MyISAM1 database table. The databse currently has thousands of records where the column value is very important. It is crucial that the current value is not affected. I want to increment from the latest higheste value.
I tried this within phpmyadmin (sql generated by phpmyadmin) and got an error.
ALTER TABLE `myTable` CHANGE `myCol1` `myCol1` INT(11) NOT NULL AUTO_INCREMENT;
The error I got was:
ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '2197' for key 'PRIMARY'
I did some reaserch and found that by adding an offset it should resolve my issue. I tried this but was greeted with a syntax error.
ALTER TABLE `myTable` CHANGE `myCol1` INT(11) NOT NULL AUTO_INCREMENT = 2500
error:
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INT(11) NOT NULL AUTO_INCREMENT = 2500' at line 1
I have also tried the above sql without declaring INT
Simply put I need to keep the existing records as they are but add auto increment ability to column myCol1 starting from number 2500 (as currently the last item is 2498). This column is also the Primary Key.
This is not a duplicate question as the solutions I have found for other answers do not resolve my issue.

You are using wrong syntax, try below command-
ALTER TABLE `myTable` CHANGE `myCol1` `myCol1` INT(11) NOT NULL AUTO_INCREMENT, auto_increment=2500;

Related

Adding new Column with current time in SQL

Im trying to add a new column to my SQL table i want the data type to be TIME and the default value to be CURRENT_TIME. This is my query.
ALTER TABLE tuesday_records ADD cur_time TIME DEFAULT CURRENT_TIME
And this is the error message i get.
Error
SQL query:
ALTER TABLE tuesday_records ADD cur_time TIME DEFAULT CURRENT_TIME
MySQL said: Documentation
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'CURRENT_TIME' at line 1
You can do what you want with generated columns:
create table t (
id int auto_increment primary key,
x int,
t timestamp default now(),
tt time generated always as (time(t))
);
That is, add a timestamp column and then extract the time.
Here is a db<>fiddle.
Although this answers your question, I'm not sure if it is the best approach to your overall problem.

Failed to set default null value for column

I already have a table, simplified example:
CREATE TABLE t (c INT NOT NULL);
And I need to change column default value to NULL, so I tried:
ALTER TABLE t ALTER COLUMN c SET DEFAULT NULL;
but I got the error "Error Code: 1067. Invalid default value for 'c'".
It looks really strange, because query conforms with official docs.
I even tried to:
ALTER TABLE t ALTER COLUMN c DROP DEFAULT;
and after it to make a 'SET DEFAULT NULL' query, but the same error occurred.
It's interesting, that query like:
ALTER TABLE t ALTER COLUMN c SET DEFAULT 1;
executed without errors.
I know, that it is possible to change column default value to NULL in my case using:
ALTER TABLE t MODIFY COLUMN c INT NULL;
but this query is really slow on big tables (it is much slower, than queries like 'SET DEFAULT 1')
So, how to just change default value to NULL?
I mean, without any overhead caused by 'MODIFY COLUMN' command.
Details: MySQL x64 version 5.7.10, Win8. Tested using MySQL Workbench.
By creating column as NOT NULL you have created a CONSTRAINT - declaring that values entered into that column may never be NULL.
A default value of NULL (set to null is value not present during INSERT) would create invalid data.
As sadly nullability constraint is part of the datatype in mysql the only way to make the column nullable will be
ALTER TABLE t MODIFY COLUMN c INT NULL;

MySQL: How to solve syntax error on ALTER TABLE statement during change type of column

When running
ALTER TABLE my_table modify column my_column int(10) NOT NULL DEFAULT 0;
I've got the error message:
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'int(10) NOT NULL DEFAULT 0' at line 1.
How can this issue being fixed?
ALTER TABLE ... MODIFY COLUMN ... does not allow renaming the column; this is why the name of the column must be provided only once (the current name).
In order to rename the column (besides other changes you may want to operate on it, like changing its type) you have to use ALTER TABLE ... CHANGE COLUMN ... and provide the current and the new name of the column.
See the documentation page of the ALTER TABLE statement for more explanation and examples.
Try this code
ALTER TABLE my_table CHANGE mycolumn my_column INT( 10 ) NOT NULL DEFAULT '1';

Can't set a default value to INT(11) altering table

I am trying to alter a table and set a default value for a nullable column. But i get the following error.
Here is the command:
ALTER TABLE `questiontboard`.`questions`
CHANGE COLUMN `status` `status` (11) NULL DEFAULT 1 ;
Here is the error:
ERROR 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(11) NULL DEFAULT 1' at line 2
SQL Statement:
ALTER TABLE `questionboard`.`questions`
CHANGE COLUMN `status` `status` (11) NULL DEFAULT 1
ERROR: Error when running failback script. Details follow.
ERROR 1050: Table 'question' already exists
What am i doing wrong?
You forgot the data type. Did you mean
ALTER TABLE `questiontboard`.`questions`
CHANGE COLUMN `status` `status` INT(11) NULL DEFAULT 1 ;
^^^
Your query should be this:
ALTER TABLE `questiontboard`.`questions`
CHANGE COLUMN `status` `status` int(11) NULL DEFAULT 1 ;
^^ here add int as you want the datatype
You are missing datatype of field in the query.
I got the same error when altering a table. I did the exact same thing you did (minus the code typo).
I got the error when altering a column from a SMALLINT to a varchar(n). It gives the "1050 Table already exists..." error. The error was confusing. Of course the table exists, that's why I'm trying to alter it!
In the end, I found out that the problem was that my new varchar(2) was not big enough to hold all the original smallint data. I had one row that had a 4 digit number, so varchar(2) wouldn't work. I changed it to use varchar(4), and it worked.
ALTER TABLE omiccom_wp.myTable
CHANGE COLUMN myColumn myColumn VARCHAR(2) NOT NULL DEFAULT '0' ;

MySql can't make column auto_increment

I have a table "Bestelling" with 4 columns: "Id" (PK), "KlantId", "Datum", "BestellingsTypeId", now I want to make the column Id auto_increment, however, when I try to do that, I get this error:
ERROR 1062: ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '1' for key 'PRIMARY'
SQL Statement:
ALTER TABLE `aafest`.`aafest_bestelling` CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT
ERROR: Error when running failback script. Details follow.
ERROR 1046: No database selected
SQL Statement:
CREATE TABLE `aafest_bestelling` (
`Id` int(11) NOT NULL,
`KlantId` int(11) DEFAULT NULL,
`Datum` date DEFAULT NULL,
`BestellingstypeId` int(11) DEFAULT NULL,
PRIMARY KEY (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
Anyone got an idea?
This will happen if the table contains an existing record with an id of 0 (or negative). Updating all existing records to use positive values will allow auto_increment to be set on that column.
Edit: Some people asked how that 0 got in there. For clarification, the MySQL Reference Manual states that "For numeric types, the default is 0, with the exception that for integer or floating-point types declared with the AUTO_INCREMENT attribute, the default is the next value in the sequence." So, if you performed an insert on a table without providing a value for the numeric column before the auto_increment was enabled, then the default 0 would be used during the insert. More details may be found at https://dev.mysql.com/doc/refman/5.0/en/data-type-defaults.html.
I also had this issue when trying to convert a column to auto_increment where one row had a value of 0. An alternative to changing the 0 value temporarily is via setting:
SET SESSION sql_mode='NO_AUTO_VALUE_ON_ZERO';
for the session.
This allowed the column to be altered to auto_increment with the zero id in place.
The zero isn't ideal - and I also wouldn't recommend it being used in an auto_increment column. Unfortunately it's part of an inherited data set so I'm stuck with it for now.
Best to clear the setting (and any others) afterwards with:
SET SESSION sql_mode='';
although it will be cleared when the current client session clsoes.
Full details on the 'NO_AUTO_VALUE_ON_ZERO' setting here.
This happens when MySQL can not determine a proper auto_increment value. In your case, MySQL choose 1 as next auto_increment value, however there is already row with that value in the table.
One way to resolve the issue is to choose a proper auto_increment value yourself:
ALTER TABLE ... CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT = 123456;
(Note the AUTO_INCREMENT=123456 at the end.)
The easiest way that I have found to solve this issue is to first set the table's AUTO INCREMENT value before altering the column. Just make sure that you set the auto increment value higher than the largest value currently in that column:
ALTER TABLE `aafest`.`aafest_bestelling`
AUTO_INCREMENT = 100,
CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT
I tested this on MySQL 5.7 and it worked great for me.
Edit: Don't know exactly how that would be caused, but I do have a workaround.
First, create a new table like the old one:
CREATE TABLE aafest_bestelling_new LIKE aafest_bestelling;
Then change the column
ALTER TABLE `aafest`.`aafest_bestelling_new`
CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT
Dump in the new data:
INSERT INTO aafest_bestelling_new
(KlantId, Datum, BestellingTypeId)
SELECT
KlantId, Datum, BestellingTypeId
FROM aafest_bestelling;
Move the tables:
RENAME TABLE
aafest_bestelling TO aafest_bestelling_old,
aafest_bestelling_new TO aafest_bestelling;
Maybe there's some corruption going on, and this would fix that as well.
P.S.: As a dutchman, I'd highly recommend coding in english ;)
I had a similar issue. Issue was the table had a record with ID = 0 similar to what SystemParadox pointed out. I handled my issue by the following steps:
Steps:
Update record id 0 to be x where x = MAX(id)+1
Alter table to set primary key and auto increment setting
Set seed value to be x+1
Change record id x back to 0
Code Example:
UPDATE foo SET id = 100 WHERE id = 0;
ALTER TABLE foo MODIFY COLUMN id INT(11) NOT NULL AUTO_INCREMENT;
ALTER TABLE foo AUTO_INCREMENT = 101;
UPDATE foo SET id = 0 WHERE id = 100;
This happens because your primary key column already has values.
As the error says ...
ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '1' for key 'PRIMARY'
which means that your column already has a primary key value 1 which when you auto_increment that column is reassigned causing duplication and hence this error
the solution to this is to remove the primary constraint and then empty the column. Then alter the table setting the primary key again, this time with auto increment.
This error comes because the any table contains an existing record with an id of 0 (or negative). Update all existing records to use positive values will allow auto_increment to be set on that column.
If this didn't work then export all the data and save it any where in you computer and dont first make foreign key relation then fill data in parent table .
This error will also happen if have a MyISAM table that has a composite AUTO_INCREMENT PRIMARY KEY and are trying to combine the keys
For example
CREATE TABLE test1 (
`id` int(11) NOT NULL,
`ver` int(10) unsigned NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`,`ver`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
INSERT INTO test1 (`id`, `ver`) VALUES (1,NULL),(1,NULL),(1,NULL), (2,NULL),(2,NULL),(2,NULL);
ALTER TABLE test1 DROP PRIMARY KEY, ADD PRIMARY KEY(`ver`);
Not being able to set an existing column to auto_increment also happens if the column you're trying to modify is included in a foreign key relation in another table (although it won't produce the error message referred to in the question).
(I'm adding this answer even though it doesn't relate to the specific error message in the body of the question because this is the first result that shows up on Google when searching for issues relating to not being able to set an existing MySQL column to auto_increment.)