So i have MySql and i have a table user with a user_id column and it is the primary key and auto incremented. Now when i delete all my data from the table and add the new one, the user_id does not start from 1 but from the number it had before deletion. What if i want to reset it without dropping the whole table and creating it again.
ALTER TABLE some_table AUTO_INCREMENT=1
So some_table would be the table you want to alter.
You could also use:
TRUNCATE TABLE some_table
This will reset the Auto Increment on the table as well as deleting all records from that table.
The code below is best if you have some data in the database already but want to reset the user_id to 1 without deleting the data. Copy and run in SQL command
ALTER TABLE members DROP user_id;
ALTER TABLE members AUTO_INCREMENT = 1;
ALTER TABLE members ADD user_id int UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY FIRST;
you can use DBCC check identity to reset your Primary key.
here is the Sytax:
DBCC CHECKIDENT(TableName,RESEED,0)
Related
I want to add a new primary key auto-incremented column with alter command but I don't want to start it with 1.
Note: My table has data for other columns so i want to add a new-column that starts its auto increment with some number other than 1.
So is there any way to achieve this with the alter command to add column.
I research, do experiments and found that this is not possible to add the new column in existing data table with auto increment that starts with number another then 1.
This can be done
ALTER TABLE my_table AUTO_INCREMENT = 1000
ALTER TABLE my_table ADD my_table_id INT PRIMARY KEY AUTO_INCREMENT FIRST;
I have a big MySQL InnoDB table having 5 million rows. I need to add a column to the table which will have a default int value.
What is the best way to do it? The normal alter table command appears to take a lot of time. Is there any better way to do it? Basically I want to know if there is any faster way or efficient way of doing it.
And if the table has foreign key references, is there any way other than alter table to do this?
Any help appreciated.
I would not say this is a better way, but ... You could create a separate table for the new data and set it up as foreign key relationship to the existing table. That would be "fast", but if the data really belongs in the main table and every (or most) existing records will have a value, then you should just alter the table and add it.
Suppose the table looked like this:
CREATE TABLE mytable
(
id INT NOT NULL AUTO_INCREMENT,
name VARCHAR(25),
PRIMARY KEY (id),
KEY name (name)
);
and you want to add an age column with
ALTER TABLE mytable ADD COLUMN age INT NOT NULL DEFAULT 0;
You could perform the ALTER TABLE in stages as follows:
CREATE TABLE mytablenew LIKE mytable;
ALTER TABLE mytablenew ADD COLUMN age INT NOT NULL DEFAULT 0;
INSERT INTO mytablenew SELECT id,name FROM mytable;
ALTER TABLE mytable RENAME mytableold;
ALTER TABLE mytablenew RENAME mytable;
DROP TABLE mytableold;
If mytable uses the MyISAM Storage Engine and has nonunique indexes, add two more lines
CREATE TABLE mytablenew LIKE mytable;
ALTER TABLE mytablenew ADD COLUMN address VARCHAR(50);
ALTER TABLE mytablenew DISABLE KEYS;
INSERT INTO mytablenew SELECT id,name FROM mytable;
ALTER TABLE mytable RENAME mytableold;
ALTER TABLE mytablenew RENAME mytable;
DROP TABLE mytableold;
ALTER TABLE mytable ENABLE KEYS;
This will let you see how many seconds each stage takes. From here, you can decide whether or not a straightforward ALTER TABLE is better.
This technique gets a little gory if there are foreign key references.
Your steps would be
SET UNIQUE_CHECKS = 0;
SET FOREIGN_KEY_CHECKS = 0;
Drop the foreign key references in mytable.
Perform the ALTER TABLE in Stages
Create the foreign key references in mytable.
SET UNIQUE_CHECKS = 1;
SET FOREIGN_KEY_CHECKS = 1;
Give it a Try !!!
Thank you in advance for your help on this one.
Here's my issue:
Table A had spam accounts that I deleted. The rows were like:
1, 2556, 2559, 2565, 2595, etc.
Am trying to import Table A into the empty Table B in the same database.
tables have different fields.
Table B declines the import because the insert is set to auto increment.
Mysql table B does not seem to want to skip rows.
I went to Table A and updated the rows to:
1, 2, 3,4,5..., 18
Now when I try to create a user in Table A using PyphAdmin with user_id value of NULL,
the id i get is 2596. Mysql still remembers the old incrementing sequence.
How can I get Mysql table to auto-increment based on the previous row so the new
id will be 19 ?
The mysql import file is encrypted in phpshield so I dont see what's
going on and has no way to edit it. But I assume this is what is happening after I ruled out all other possibilities.
The field must be primary key - PRIMARY KEY (id)
The field must be AUTO_INCREMENT
Reset table's autoincrement value.
For example -
CREATE TABLE table1(
id INT(11) NOT NULL AUTO_INCREMENT,
PRIMARY KEY (id)
);
Set new autoincrement value -
ALTER TABLE table1 AUTO_INCREMENT = 19;
Try this
ALTER TABLE A AUTO_INCREMENT=19;
ALTER TABLE TableA
AUTO_INCREMENT=19;
How do I add auto_increment to an existing column of a MySQL table?
I think you want to MODIFY the column as described for the ALTER TABLE command. It might be something like this:
ALTER TABLE users MODIFY id INTEGER NOT NULL AUTO_INCREMENT;
Before running above ensure that id column has a Primary index.
Method to add AUTO_INCREMENT to a table with data while avoiding “Duplicate entry” error:
Make a copy of the table with the data using INSERT SELECT:
CREATE TABLE backupTable LIKE originalTable;
INSERT backupTable SELECT * FROM originalTable;
Delete data from originalTable (to remove duplicate entries):
TRUNCATE TABLE originalTable;
To add AUTO_INCREMENT and PRIMARY KEY
ALTER TABLE originalTable ADD id INT PRIMARY KEY AUTO_INCREMENT;
Copy data back to originalTable (do not include the newly created column (id), since it will be automatically populated)
INSERT originalTable (col1, col2, col3)
SELECT col1, col2,col3
FROM backupTable;
Delete backupTable:
DROP TABLE backupTable;
More on the duplication of tables using CREATE LIKE:
Duplicating a MySQL table, indices, and data
Alter table table_name modify column_name datatype(length) AUTO_INCREMENT PRIMARY KEY
You should add primary key to auto increment, otherwise you got error in mysql.
Simply just add auto_increment Constraint In column or MODIFY COLUMN :-
ALTER TABLE `emp` MODIFY COLUMN `id` INT NOT NULL UNIQUE AUTO_INCREMENT FIRST;
Or add a column first then change column as -
1. Alter TABLE `emp` ADD COLUMN `id`;
2. ALTER TABLE `emp` CHANGE COLUMN `id` `Emp_id` INT NOT NULL UNIQUE AUTO_INCREMENT FIRST;
This worked for me in case you want to change the AUTO_INCREMENT-attribute for a not-empty-table:
1.)Exported the whole table as .sql file
2.)Deleted the table after export
2.)Did needed change in CREATE_TABLE command
3.)Executed the CREATE_TABLE and INSERT_INTO commands from the .sql-file
...et viola
I managed to do this with the following code:
ALTER TABLE `table_name`
CHANGE COLUMN `colum_name` `colum_name` INT(11) NOT NULL AUTO_INCREMENT FIRST;
This is the only way I could make a column auto increment.
INT(11) shows that the maximum int length is 11, you can skip it if you want.
Alter table table_name modify table_name.column_name data_type AUTO_INCREMENT;
eg:
Alter table avion modify avion.av int AUTO_INCREMENT;
if you have FK constraints and you don't want to remove the constraint from the table. use "index" instead of primary. then you will be able to alter it's type to auto increment
I had existing data in the first column and they were 0's.
First I made the first column nullable.
Then I set the data for the column to null.
Then I set the column as an index.
Then I made it a primary key with auto incrementing turned on. This is where I used another persons answer above:
ALTER TABLE `table_name` CHANGE COLUMN `colum_name` `colum_name` INT(11) NOT NULL AUTO_INCREMENT FIRST;
This Added numbers to all the rows of this table starting at one. If I ran the above code first it wasn't working because all the values were 0's. And making it an index was also required before making it auto incrementing.
Next I made the column a primary key.
This worked in my case , if you want to change the column attribute to auto-increment which is already having some data
1.GO to structure, select the column to want to change.
2.After selecting the column , choose primary key from the options below.
[1]: https://i.stack.imgur.com/r7w8f.png
3.Then change the column attribute to auto-increment using alter method
This is to alter the column adding PRIMARY key:
ALTER TABLE `schema_name`.`table_name`
CHANGE COLUMN `id` `id` INT(11) NOT NULL AUTO_INCREMENT ,
ADD UNIQUE INDEX `id_UNIQUE` (`id` ASC) VISIBLE,
ADD PRIMARY KEY (`id`);
I copied it from MySQL Workbench... I got curious to see if it was possible to do it all in one command. I'm a little rusty in SQL.
If you are working in an specific schema, you don't need to specify it.
The above statement will create the index, set the column as the PRIMARY KEY as well with just one query.
KEEP IN MIND: There could not be duplicated values in the same column, if there are, the statement will fail to commit.
ALTER TABLE Table name ADD column datatype AUTO_INCREMENT,ADD primary key(column);
I am using SQLite3. I load a table with say 30 rows using integer as Primary ID and it auto-increments.
Now I delete all the rows from the table and then, reload some new information onto the table.
Problem is: the row count (my PrimaryID) now starts with 31. Is there any way that I can start loading new rows from the number 1 onwards?
SQLite
Use:
DELETE FROM your_table;
DELETE FROM sqlite_sequence WHERE name = 'your_table';
Documentation
SQLite keeps track of the largest ROWID that a table has ever held using the special SQLITE_SEQUENCE table. The SQLITE_SEQUENCE table is created and initialized automatically whenever a normal table that contains an AUTOINCREMENT column is created. The content of the SQLITE_SEQUENCE table can be modified using ordinary UPDATE, INSERT, and DELETE statements. But making modifications to this table will likely perturb the AUTOINCREMENT key generation algorithm. Make sure you know what you are doing before you undertake such changes.
Found the answer on SO: SQLite Reset Primary Key Field
MySQL
Use:
ALTER TABLE tbl AUTO_INCREMENT = 1;
In either case, the database doesn't care if the id numbers are sequencial - only that the values are unique. If users never see the primary key value (they shouldn't, because the data can change & won't always be at that primary key value), I wouldn't bother with these options.
For MySQL:
Use TRUNCATE TABLE tablename to empty the table (delete all records) and reset auto increment count.
You can also use ALTER TABLE tablename AUTO_INCREMENT = 0; if you just want to reset the count.
For SQLite:
DELETE FROM tablename;
DELETE FROM SQLITE_SEQUENCE WHERE name='tablename';
References
SQLite AutoIncrement
MySQL AutoIncrement
For SQLite use (not need to delete and create the table)
UPDATE SQLITE_SEQUENCE SET SEQ=0 WHERE NAME='table_name';
For MySql use
ALTER TABLE table_name AUTO_INCREMENT = 1;
You should not use AUTOINCREMENT in this case. Simply define your primary key as INTEGER PRIMARY KEY and the count will be reset to 1 after a DELETE FROM query. Without AUTOINCREMENT, the default behaviour will still be an automatic increment of the primary key as long as you don't run out of space in your table (in that case, old - deleted - values will be reused).
More information available in the SQLite Autoincrement document.
ALTER TABLE tbl AUTO_INCREMENT = 0;