MYSQL SEQUENCE (Lab2.2) - MYSQL SEQUENCE Summary in this...

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MYSQL SEQUENCE Summary : in this tutorial, we will show you how to use MySQL sequence to automatically generate unique numbers for ID columns of tables. MySQL create sequence In MySQL, a sequence is a list of integers generated in the ascending order i.e., 1,2,3… Many applications need sequences to generate unique numbers mainly for identification e.g., customer ID in CRM, employee number in HR, equipment number in services management system, etc. To create a sequence in MySQL automatically, you set the AUTO_INCREMENT attribute to a column, which typically is primary key column. The following are rules that you must follow when you use AUTO_INCREMENT attribute: Each table has only one AUTO_INCREMENT column whose data type is typically integer or float which is very rare. The AUTO_INCREMENT column must be indexed, which means it can be either PRIMARY KEY or UNIQUE index. The AUTO_INCREMENT column must have NOT NULL constraint. When you set AUTO_INCREMENT attribute to a column, MySQL will make it NOT NULL for you in case you don’t define it explicitly. MySQL create sequence example The following example creates employees table whose emp_no column is AUTO_INCREMENT column: 1 2 3 4 5 CREATE TABLE employees(
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