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Where to put the auto increment key in MySQL?
The auto_increment will function normally after that without any problems. You should also place a unique key on the auto_increment field as well, to use for your row handling: Thanks for contributing an answer to Stack Overflow!
How to convert primary key to auto increment?
ERROR 1062: ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry ‘1’ for key ‘PRIMARY’ SQL Statement: ALTER TABLE `Clinic`.`ClientSupplementary` CHANGE COLUMN `idClientSupplementary` `idClientSupplementary` INT(11) NOT NULL AUTO_INCREMENT ERROR: Error when running failback script. Details follow.
How to set auto increment to null in MySQL?
Set the auto increment field to NULL or 0 if you want it to be auto magically assigned… I’m running mysql –version 5.1.66: No value was specified for the AUTO_INCREMENT column, so MySQL assigned sequence numbers automatically. You can also explicitly assign NULL or 0 to the column to generate sequence numbers.
Which is an example of an auto increment column?
This is by design – all DBMS act this was with auto-increment columns. If they did not external referential integrity could be damaged. For a simple example of this, imagine you are storing URLs for a shortening service using an auto-increment column as the key.
When do you not need an auto increment key?
Other cases when a surrogate auto-increment key is not needed: You already have a combination of other columns (whether they are surrogate keys or natural keys) that provides a candidate key for the table. A good example is found in many-to-many tables.
Can a primary key be auto incremented in a database?
The answer to (3) depends on whether you need to generate keys independently from the database (e.g. while disconnected, or while connected to a different database). If yes, you could use GUIDs (which obviously cannot be auto-incremented, but can be uniquely generated in isolation).
Can a table have more than one auto increment?
There can be only one AUTO_INCREMENT column per table, it must be indexed, and it cannot have a DEFAULT value. So you can indeed have an AUTO_INCREMENT column in a table that is not the primary key. If that makes sense, is a different topic though.