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Description

Error 1853 in MariaDB indicates an attempt to drop an existing primary key from a table without simultaneously defining a new primary key in the same `ALTER TABLE` statement. MariaDB, like MySQL, often enforces the presence of a primary key for data integrity, uniqueness, and efficient row identification. This error typically arises during schema modifications where the primary key constraint is being altered or removed.

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Error Message

Dropping a primary key is not allowed without also adding a new primary key

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Known Causes

4 known causes

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Malformed ALTER TABLE Statement

The SQL statement attempts to `DROP PRIMARY KEY` without including an `ADD PRIMARY KEY` clause for a new primary key in the same command.

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Primary Key Requirement Misconception

Users might not be aware that MariaDB often implicitly requires a primary key, especially when strict SQL modes are enabled, preventing tables from existing without one.

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Removing Sole Unique Identifier

The primary key is frequently the only unique index on a table. Removing it without a replacement can violate data integrity principles or break application dependencies.

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Scripting Error or Oversight

In complex schema migration scripts, the clause to add a new primary key might have been accidentally omitted, leading to this error during execution.

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Solutions

3 solutions available

1. Add a New Primary Key Simultaneously easy

Recreate the primary key immediately after dropping it in the same transaction.

1

Begin a transaction to ensure atomicity. If the drop fails, the add will also be rolled back.

START TRANSACTION;

2

Drop the existing primary key. Replace `your_table_name` with the actual table name.

ALTER TABLE your_table_name DROP PRIMARY KEY;

3

Add a new primary key. Replace `your_table_name`, `new_primary_key_column`, and `pk_constraint_name` with your specific details. The new primary key must be on one or more existing columns that together uniquely identify each row.

ALTER TABLE your_table_name ADD PRIMARY KEY (new_primary_key_column);

4

Commit the transaction to apply the changes.

COMMIT;

2. Define a New Primary Key Before Dropping medium

Identify and define the new primary key column(s) before attempting to remove the old one.

1

Identify the column(s) that will serve as the new primary key. These columns must contain unique, non-NULL values for every row.

2

Verify that the chosen column(s) have unique and non-NULL values. If not, you'll need to clean up the data first.

SELECT COUNT(column_name) FROM your_table_name WHERE column_name IS NULL;
SELECT COUNT(column_name), column_name FROM your_table_name GROUP BY column_name HAVING COUNT(column_name) > 1;

3

Begin a transaction.

START TRANSACTION;

4

Add the new primary key. Replace `your_table_name` and `new_primary_key_column`.

ALTER TABLE your_table_name ADD PRIMARY KEY (new_primary_key_column);

5

Drop the old primary key. Replace `your_table_name`.

ALTER TABLE your_table_name DROP PRIMARY KEY;

6

Commit the transaction.

COMMIT;

3. Create a New Table with the Desired Primary Key advanced

A more involved approach to restructure the table and define the primary key during creation.

1

Create a new table with the same schema as the original, but define the new primary key during creation. Replace `new_table_name`, `your_table_name`, and `new_primary_key_column`.

CREATE TABLE new_table_name LIKE your_table_name;
ALTER TABLE new_table_name ADD PRIMARY KEY (new_primary_key_column);

2

Copy data from the old table to the new table. Ensure the `new_primary_key_column` values are unique and non-NULL in the source data.

INSERT INTO new_table_name SELECT * FROM your_table_name;

3

Verify the data in the new table, especially the primary key column for uniqueness and completeness.

4

Rename the original table to a backup name.

RENAME TABLE your_table_name TO your_table_name_backup;

5

Rename the new table to the original table's name.

RENAME TABLE new_table_name TO your_table_name;

6

Optional: Drop the backup table after confirming everything is working correctly.

DROP TABLE your_table_name_backup;

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Related Errors

5 related errors

MariaDB Error 1853: Dropping Primary Key Without Replacement