<p>MySQL throws Error 1586 when an INSERT or UPDATE generates a duplicate value for a column or index declared UNIQUE or PRIMARY KEY.</p>
<p>MySQL Error 1586: ER_DUP_ENTRY_WITH_KEY_NAME means an INSERT or UPDATE tried to write a value that already exists in a UNIQUE or PRIMARY KEY index. Remove or change the duplicate value, or use INSERT ... ON DUPLICATE KEY UPDATE to fix the problem.</p>
Duplicate entry '%s' for key '%s'
MySQL error 1586, ER_DUP_ENTRY_WITH_KEY_NAME, indicates that an INSERT or UPDATE statement tried to create a row whose key value already exists in a column or group of columns defined as UNIQUE or PRIMARY KEY. MySQL blocks the write to preserve data integrity, returning Duplicate entry '%s' for key '%s'.
The duplicate entry error fires during INSERT ... VALUES, INSERT ... SELECT, LOAD DATA, REPLACE, or UPDATE statements whenever the new data conflicts with an existing unique index or primary key value. It can also appear after ALTER TABLE ... ADD UNIQUE when duplicated data already resides in the table.
Leaving duplicate entry errors unresolved stops data ingestion workflows, breaks application logic that expects successful writes, and can cascade into lost transactions or inconsistent reports. Rapid remediation keeps pipelines healthy and protects referential integrity.
Most occurrences trace back to missing deduplication logic, race conditions in concurrent inserts, or improper assumptions about auto increment values. Import tools that skip validation can also inject duplicates.
The fastest remedy is correcting or deleting the conflicting row, then rerunning the statement. Alternatively, modify the INSERT to ignore duplicates or update existing rows. In rare edge cases, rebuild the unique index after cleansing data.
During bulk loads, run SELECT key_column, COUNT(*) FROM table GROUP BY key_column HAVING COUNT(*) > 1 to locate offenders. For high-traffic APIs, wrap inserts in INSERT ... ON DUPLICATE KEY UPDATE to make operations idempotent.
Validate data before loading, enforce unique constraints early in development, and use transactions with proper isolation levels. Application-side upserts and Galaxy's query history help developers spot patterns that create duplicates.
Errors 1062, 1558, and 1022 involve similar unique-constraint violations but differ in context. Fixes mirror those for 1586: locate duplicates, adjust data, or change the statement to upsert.
Two sessions insert identical key values almost simultaneously, causing the second insert to violate the unique index.
Bulk LOAD DATA or ETL jobs bypass prior checks and copy duplicate rows into the target table.
Applications or scripts inadvertently reuse primary key values or forget to increment surrogate keys.
Resetting AUTO_INCREMENT to a lower value causes new rows to overlap with existing keys.
Raised for generic duplicate value conflicts without specifying the index name.
Occurs when a primary key column receives NULL instead of a duplicate.
Appears during ALTER TABLE or CREATE INDEX when building a unique index on non-unique data.
Use INSERT IGNORE or set sql_mode='IGNORE_SPACE' to skip conflicting rows, but this hides data problems. Upserts are safer.
Dropping the unique index eliminates the constraint, but you lose data integrity. Only drop it temporarily while cleansing duplicates.
Run GROUP BY queries on the indexed columns with HAVING COUNT(*) > 1, or use Galaxy's AI copilot to generate deduplication SQL automatically.
Yes. Galaxy surfaces constraint definitions in autocomplete, warns about duplicate insert patterns, and offers one-click upsert templates.
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