Thursday, April 12, 2012

MySQL - ignore insert error: duplicate entry

I am working in PHP.

Please what's the proper way of inserting new records into the DB, which has unique field. I am inserting lot of records in a batch and I just want the new ones to be inserted and I don't want any error for the duplicate entry.

Is there only way to first make a SELECT and to see if the entry is already there before the INSERT - and to INSERT only when SELECT returns no records? I hope not.

I would like to somehow tell MySQL to ignore these inserts without any error.

Thank you

Source: Tips4all


  1. You can use INSERT... IGNORE syntax if you want to take no action when there's a duplicate record.

    You can use REPLACE INTO syntax if you want to overwrite an old record with a new one with the same key.

    Or, you can use INSERT... ON DUPLICATE KEY UPDATE syntax if you want to perform an update to the record instead when you encounter a duplicate.

    Edit: Thought I'd add some examples.


    Say you have a table named tbl with two columns, id and value. There is one entry, id=1 and value=1. If you run the following statements:

    REPLACE INTO tbl VALUES(1,50);

    You still have one record, with id=1 value=50. Note that the whole record was DELETED first however, and then re-inserted. Then:


    The operation executes successfully, but nothing is inserted. You still have id=1 and value=50. Finally:


    You now have a single record with id=1 and value=200.

  2. You can use triggers.

    Also check this introduction guide to triggers.

  3. Try creating a duplicate table, preferably a temporary table, without the unique constraint and do your bulk load into that table. Then select only the unique (DISTINCT) items from the temporary table and insert into the target table.

  4. What does the database schema look like?

    You could add an ID column which will auto increment for each insert, to guarantee unique rows.

  5. Question: I am setting up a database with clients. I know that you use the "insert" statement to insert information in the database, but how do I make sure that I do not enter the same client information again?

    Answer: You can make sure that you do not insert duplicate information by using the EXISTS condition.

    For example, if you had a table named clients with a primary key of client_id, you could use the following statement:

    INSERT INTO clients
    (client_id, client_name, client_type)
    SELECT supplier_id, supplier_name, 'advertising'
    FROM suppliers
    WHERE not exists (select * from clients
    where clients.client_id = suppliers.supplier_id);

    This statement inserts multiple records with a subselect.

    If you wanted to insert a single record, you could use the following statement:

    INSERT INTO clients
    (client_id, client_name, client_type)
    SELECT 10345, 'IBM', 'advertising'
    FROM dual
    WHERE not exists (select * from clients
    where clients.client_id = 10345);

    The use of the dual table allows you to enter your values in a select statement, even though the values are not currently stored in a table.