Why am I getting the duplicate entry error when there are no duplicates?

921 Asked by DavidWHITE in SQL Server , Asked on Feb 7, 2023

I keep getting this error:

failed to INSERT: [1062] Duplicate entry 'Upping Your Type Game-http://jessicahische.is/talkingtype' for key 'PRIMARY'.

The problem is that there are no duplicate entries. Which is why I'm confused when receiving that error.

Is there any way to check using InnoDB?

I have tried exporting the table and reading the SQL code and ran a search for any duplicates but there wasn't any.

Answered by elonjigar

It isn't saying that there is a duplicate entry in the table already, it is saying that there is already one entry in there with that value for the primary key and it is refusing to insert a second for that reason.

I suspect if you run:

SELECT * 

FROM    

WHERE   = 'Upping Your Type Game-http://jessicahische.is/talkingtype'

or if that key is a composite

SELECT * 

FROM    

WHERE   = 'Upping Your Type Game' 

AND     = 'http://jessicahische.is/talkingtype'

You will find one matching row, and that your code at the point of the error is trying to insert a second.

Dealing with duplicates on insert:

If you try to INSERT duplicate values for a primary key (or a unique index) you will always get that error. There are a couple of ways around it: check before you insert and either do an update (if something might have changed) or just don't do anything.

There is also the mysql specific ON DUPLICATE KEY UPDATE option (see https://stackoverflow.com/questions/1218905/how-do-i-update-if-exists-insert-if-not-aka-upsert-or-merge-in-mysql) if you are happy to sacrifice compatibility with other RDBMSs.

As of version 9.5 Postgres supports a similar feature with slightly different syntax (ON CONFLICT DO UPDATE/NOTHING - see https://wiki.postgresql.org/wiki/UPSERT).

MS SQL Server, Oracle and some other systems support MERGE statements as defined in the SQL:2003 standard (see https://en.wikipedia.org/wiki/Merge_(SQL)) which is intended to achieve the same functionality and more. Be careful with any of these options if cross database compatibility is (or is likely to be in future) one of your goals.

Your Answer

Answer (1)

Ranjana

The "Duplicate Entry" error in a database typically occurs when you're trying to insert a record that violates a unique constraint. This is common with primary keys or unique indexes. Here are several potential reasons why you might encounter this error even if there appear to be no duplicates:

Index Issues:

There may be an existing unique index on one or more columns that you are unaware of. Ensure that the column(s) you're inserting into do not have a unique constraint that you might be inadvertently violating.

Case Sensitivity:

Some databases are case-sensitive when it comes to unique constraints, while others are not. Make sure that the data you're inserting does not differ only in case from existing entries.

Trailing Spaces:

Trailing spaces in text fields can sometimes cause duplicate entry issues. For example, "value" and "value " would be considered different in some databases but might cause issues in others.

Concurrent Inserts:

If multiple processes or transactions are inserting data at the same time, there could be a race condition where two transactions are attempting to insert the same value simultaneously. Use transactions properly to avoid such conflicts.

Data Anomalies:

Ensure that there are no hidden characters or invisible differences in the data that could cause the database to see them as identical. This can include things like invisible Unicode characters or non-printing characters.

Database Collation:

The collation settings of your database can affect how it treats string comparisons. Check the collation settings to ensure that they are as expected.

Check for Invisible Characters:

SELECT id, column_name, LENGTH(column_name), LENGTH(TRIM(column_name))

FROM table_name

WHERE LENGTH(column_name) != LENGTH(TRIM(column_name));

By systematically checking these potential issues, you should be able to identify the cause of the duplicate entry error. If the problem persists, please provide more details about your database schema, the specific error message, and any relevant SQL queries you're running.

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