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Description

Error 1846 indicates that a requested SQL operation, often an ALTER statement, is not supported by your current MariaDB server or its configuration. This usually happens when attempting to use a feature, syntax, or storage engine option that is either deprecated, not implemented, or incompatible with the current setup.

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Error Message

%s is not supported. Reason: %s. Try %s.

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Known Causes

3 known causes

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Unsupported SQL Feature

The SQL statement attempts to use a feature, keyword, or syntax that is not implemented or supported by your current MariaDB server version.

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Storage Engine Limitation

The attempted operation is incompatible with the storage engine of the table being modified, or the engine does not support the requested feature.

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Version Incompatibility

The feature or syntax used in the SQL statement is either deprecated in your MariaDB version or was introduced in a newer version.

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Solutions

3 solutions available

1. Simplify the ALTER TABLE Statement easy

Break down complex ALTER TABLE operations into simpler, supported steps.

1

Examine the error message carefully. It will usually indicate which specific part of your `ALTER TABLE` statement is unsupported. For example, if you're trying to change the `default` value of a column and the error message suggests an alternative, you'll need to adjust your statement.

2

If you are performing multiple operations in a single `ALTER TABLE` statement (e.g., `ADD COLUMN`, `MODIFY COLUMN`, `DROP COLUMN`), try to separate them into individual `ALTER TABLE` statements. This can help isolate the problematic operation.

-- Example of breaking down a complex ALTER TABLE
-- Original (potentially problematic):
-- ALTER TABLE my_table ADD COLUMN new_col INT DEFAULT 0, MODIFY COLUMN existing_col VARCHAR(255) NOT NULL;

-- Separated into individual statements:
ALTER TABLE my_table ADD COLUMN new_col INT DEFAULT 0;
ALTER TABLE my_table MODIFY COLUMN existing_col VARCHAR(255) NOT NULL;

3

Consult the MariaDB documentation for the specific version you are using to confirm the supported `ALTER TABLE` operations and syntax for the action you are attempting.

2. Recreate the Table with Desired Schema medium

For unsupported schema changes, create a new table with the correct schema and migrate data.

1

Create a new table with the desired schema, including all the columns, indexes, and constraints you need. Ensure the new table's definition is valid and uses supported features.

-- Example: Creating a new table with a new default value
CREATE TABLE my_table_new (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    status VARCHAR(50) DEFAULT 'active'
);

2

Copy the data from the original table to the new table. Use an `INSERT INTO ... SELECT FROM` statement for this.

INSERT INTO my_table_new (id, name, status)
SELECT id, name, status FROM my_table;

3

Rename the original table to a backup name.

RENAME TABLE my_table TO my_table_old;

4

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

RENAME TABLE my_table_new TO my_table;

5

Verify that all data has been migrated correctly and that the new table functions as expected.

6

Once confirmed, you can drop the old table (`my_table_old`) at a later time.

DROP TABLE my_table_old;

3. Check MariaDB Version and Documentation for Specific Operations easy

Understand version-specific limitations and consult official documentation.

1

Determine the exact version of MariaDB you are running. You can do this with the following command:

SELECT VERSION();

2

Search the official MariaDB documentation for your specific version and the `ALTER TABLE` statement you are trying to execute. The documentation will detail supported operations and any known limitations.

3

Pay close attention to the 'Reason' part of the error message. It often hints at what is not supported and what alternatives might exist. For example, it might say 'changing default value for this data type is not supported directly' and suggest creating a new column or using a different approach.

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Related Errors

5 related errors

MariaDB Error 1846: Unsupported ALTER Operation