![]() ![]() There you go, we got now separate sequences for each of the customers.I've migrated a database from MySQL 5.3 to 8 and an odd behavior emerged. Insert into mydevices(CustomerId, DeviceName) VALUES (4,'Laptop') Insert into mydevices(CustomerId, DeviceName) VALUES (4,'Printer') Insert into mydevices(CustomerId, DeviceName) VALUES (3,'Printer') Lets now insert data to this table (we will add a few more inserts that before) UpdatedAt datetime NOT NULL DEFAULT CURRENT_TIMESTAMP, Lets create the table now as a MyISAM table Lets adapt this to the above example of MyDevices table. This is useful when you want to put data into ordered groups. If we define tables either as MyISAM or BDB, it gives the ability to specify AUTO_INCREMENT on a secondary column in a multiple-column index.įor such tables, the generated value for the AUTO_INCREMENT column is calculated as MAX(auto_increment_column) + 1 WHERE prefix=given-prefix. It is based on the older ISAM code, but it has many useful extensions. The default engine storage for MySQL relational database management system prior to versions prior to 5.5 was MyISAM. But let us see today a very easy method to achieve this, by defining the table in a certain way. There are many ways to do this such as using stored procedures. While Customer 2 devices gets a sequence number again from 1,2,3. That is each customer has its own sequence numbers for the devices. What if we want the sequence number to increase per customer. ![]() (1,2,3,4,5,6)īut what if this is not the behavior we want. Insert into mydevices(CustomerId, DeviceName) VALUES (2,'Printer') Īs you will see, the auto increment feature keeps on adding the sequences number for each row as we insert. Insert into mydevices(CustomerId, DeviceName) VALUES (2,'Laptop') Insert into mydevices(CustomerId, DeviceName) VALUES (2,'Tablet') Insert into mydevices(CustomerId, DeviceName) VALUES (1,'Phone') Insert into mydevices(CustomerId, DeviceName) VALUES (1,'Computer') Insert into mydevices(CustomerId, DeviceName) VALUES (1,'Laptop') Lets Add a few rows, to see that the sequences are working as we want. Lets drop the Devices table and recreate it as follows ĭeviceId int NOT NULL PRIMARY KEY AUTO_INCREMENT, Lets add one more column, say CustomerId in the above table. If we do a query on our table we should find that MySQL have added a nice Sequences number to our DeviceId column Insert into mydevices(DeviceName) VALUES ('Tablet') Insert into mydevices(DeviceName) VALUES ('Phone') Insert into mydevices(DeviceName) VALUES ('Computer') Insert into mydevices(DeviceName) VALUES ('Laptop') Lets Add a few rows, to see that the sequencing is working as we want. UpdatedAt datetime NOT NULL DEFAULT CURRENT_TIMESTAMPĮxecuting this gives us the table MyDevices ![]() The MySQL statement to create the table Device is given belowĭeviceId int PRIMARY KEY NOT NULL AUTO_INCREMENT,ĬreatedAt datetime NOT NULL DEFAULT CURRENT_TIMESTAMP, ![]() Here we have a table Mydevices that stores different devices we have such as laptop, computer, cellphone, tablet and so on. AUTO_INCREMENT attribute is generally used to generate a unique number that act as a primary key in a table. MySQL provides us with AUTO_INCREMENT attribute that allows us to create a column that contains a sequence of numbers (1, 2, 3, and so on). ![]()
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