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Is there a way of removing record on duplicate key in MySQL?
Say we have a record in the database with the specific primary key and we try to add another one with the same key - ON DUPLICATE KEY UPDATE would simply update the record, but is there an option to remove record if already exists? It is for simple in/out functionality on click of a button.
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The Insert on Duplicate Key Update statement is the extension of the INSERT statement in MySQL. When we specify the ON DUPLICATE KEY UPDATE clause in a SQL statement and a row would cause duplicate error value in a UNIQUE or PRIMARY KEY index column, then updation of the existing row occurs.
Note − Use the INSERT IGNORE command rather than the INSERT command. If a record doesn't duplicate an existing record, then MySQL inserts it as usual. If the record is a duplicate, then the IGNORE keyword tells MySQL to discard it silently without generating an error.
Answer: No it is not possible. The wording Primary Key imply non duplicate values, it is by design ! You can have duplicate values in Non Primary Key, it is the only way.
Preventing Duplicates from Occurring in a Table. You can use a PRIMARY KEY or a UNIQUE Index on a table with the appropriate fields to stop duplicate records. Let us take an example – The following table contains no such index or primary key, so it would allow duplicate records for first_name and last_name.
It's a work-around, but it works:
Create a new column and call it do_delete, or whatever, making it a tiny-int. Then do On Duplicate Key Update do_delete = 1;
Depending on your MySQL version/connection, you can execute multiple queries in the same statement. However, if not, just run a separate query immediately afterwords. Either way, the next query would just be: Delete From [table] Where do_delete = 1;. This way, if its a new entry, it will not delete anything. If it was not a new entry, it will then mark it for deletion then you can delete it.
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