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How to ensure that MySQL rows are unique?
To ensure that MySQL rows are unique, you need to use UNIQUE constraint. Let us first create a table −
mysql> create table DemoTable1580 -> ( -> id int, -> Name varchar(20), -> Age int -> ); Query OK, 0 rows affected (0.73 sec)
Here is the query to create unique constraints to ensure MySQL rows are unique −
mysql> alter table DemoTable1580 add unique index(id,Name,Age); Query OK, 0 rows affected (0.45 sec) Records: 0 Duplicates: 0 Warnings: 0
Insert some records in the table using insert command −
mysql> insert into DemoTable1580 values(101,'Chris',21); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable1580 values(102,'Chris',21); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1580 values(102,'David',21); Query OK, 1 row affected (0.49 sec) mysql> insert into DemoTable1580 values(101,'Chris',21); ERROR 1062 (23000): Duplicate entry '101-Chris-21' for key 'id'
Display all records from the table using select statement −
mysql> select * from DemoTable1580;
This will produce the following output −
+------+-------+------+ | id | Name | Age | +------+-------+------+ | 101 | Chris | 21 | | 102 | Chris | 21 | | 102 | David | 21 | +------+-------+------+ 3 rows in set (0.00 sec)
Updated on: 16-Dec-2019
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