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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

bakkal
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neon
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  • insert ignore works for me The problem am having some rows are deleted from table and am trying to insert the rows same id which were deleted previously in that case "insert ignore" statement worked – Balaji Jun 06 '17 at 03:56

5 Answers5

189

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.

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:

INSERT IGNORE INTO tbl VALUES (1,10);

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

INSERT INTO tbl VALUES (1,200) ON DUPLICATE KEY UPDATE value=200;

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

zombat
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    "If you use the IGNORE keyword, errors that occur while executing the INSERT statement are treated as warnings instead." -from the above insert link – gradbot May 01 '09 at 17:57
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    Warnings do not raise an error however, so your script will continue to execute. From the manual: If you use the IGNORE keyword, errors that occur while executing the INSERT statement are treated as warnings instead. For example, without IGNORE, a row that duplicates an existing UNIQUE index or PRIMARY KEY value in the table causes a duplicate-key error and the statement is aborted. With IGNORE, the row still is not inserted, but no error is issued. – zombat May 01 '09 at 17:58
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    `IGNORE` will ignore errors that may have nothing to do with duplicate keys. It's better to do `ON DUPLICATE KEY UPDATE field=field` so you can catch those errors and as a bonus, not have any warnings. – Chinoto Vokro Mar 04 '16 at 00:35
-1

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.

from http://www.techonthenet.com/sql/insert.php

gehsekky
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  • This is not the proper way to do this. This solution is slow, harder to maintain and prone to errors. Using INSERT with IGNORE would be a much better solution. – womp May 01 '09 at 18:00
  • This appears to be a Cartesian Join, which is not advised in this circumstance. –  May 08 '19 at 23:20
-2

You can use triggers.

Also check this introduction guide to triggers.

Kirtan
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-3
$duplicate_query=mysql_query("SELECT * FROM student") or die(mysql_error());
$duplicate=mysql_num_rows($duplicate_query);
if($duplicate==0)
{
    while($value=mysql_fetch_array($duplicate_query)
    {
        if(($value['name']==$name)&& ($value['email']==$email)&& ($value['mobile']==$mobile)&& ($value['resume']==$resume))
        {
            echo $query="INSERT INTO student(name,email,mobile,resume)VALUES('$name','$email','$mobile','$resume')";
            $res=mysql_query($query);
            if($query)
            {
                echo "Success";
            }
            else
            {
                echo "Error";
            }
            else
            {
                echo "Duplicate Entry";
            }
        }
    }
}
else
{
    echo "Records Already Exixts";
}
chandrasekar
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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.

Jordan S. Jones
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