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Is it compulsory to set PRIMARY KEY for AUTO_INCREMENT value?
Yes, use AUTO_INCREMENT with PRIMARY KEY. Let us first create a table −
mysql> create table DemoTable ( EmployeeId int NOT NULL AUTO_INCREMENT, EmployeeName varchar(40), EmployeeAge int, PRIMARY KEY(EmployeeId), UNIQUE KEY(EmployeeName,EmployeeAge) ); Query OK, 0 rows affected (0.96 sec)
Let us check the table description of the table −
mysql> desc DemoTable;
This will produce the following output −
+--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+----------------+ | EmployeeId | int(11) | NO | PRI | NULL | auto_increment | | EmployeeName | varchar(40) | YES | MUL | NULL | | | EmployeeAge | int(11) | YES | | NULL | | +--------------+-------------+------+-----+---------+----------------+ 3 rows in set (0.17 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Chris',25);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Robert',34);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Mike',32);
Query OK, 1 row affected (0.09 sec)Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+------------+--------------+-------------+ | EmployeeId | EmployeeName | EmployeeAge | +------------+--------------+-------------+ | 1 | Chris | 25 | | 3 | Mike | 32 | | 2 | Robert | 34 | +------------+--------------+-------------+ 3 rows in set (0.00 sec)
Updated on: 04-Oct-2019
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