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How to avoid inserting duplicate rows in MySQL?
To avoid inserting duplicate rows in MySQL, you can use UNIQUE(). The syntax is as follows −
ALTER TABLE yourTableName ADD UNIQUE(yourColumnName1,yourColumnName2,...N);
To understand the above syntax, let us create a table.
The query to create a table is as follows −
mysql> create table avoidInsertingDuplicateRows -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstValue int, -> SecondValue int -> ); Query OK, 0 rows affected (0.53 sec)
Now check the description of table using desc command.
The query is as follows −
mysql> desc avoidInsertingDuplicateRows;
Sample The following is The output −
+-------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+---------+------+-----+---------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | FirstValue | int(11) | YES | | NULL | | | SecondValue | int(11) | YES | | NULL | | +-------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec)
Here is the query to avoid inserting duplicate rows in MySQL. We will set it with the insert command to insert records in the table −
mysql> insert into avoidInsertingDuplicateRows(FirstValue,SecondValue) values(10,20); Query OK, 1 row affected (0.24 sec) mysql> insert into avoidInsertingDuplicateRows(FirstValue,SecondValue) values(10,20); ERROR 1062 (23000): Duplicate entry '10-20' for key 'FirstValue'
Display all records from the table using select statement.
The query is as follows −
mysql> select *from avoidInsertingDuplicateRows;
Here is the output −
+----+------------+-------------+ | Id | FirstValue | SecondValue | +----+------------+-------------+ | 1 | 10 | 20 | +----+------------+-------------+ 1 row in set (0.00 sec)
Updated on: 30-Jul-2019
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