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Description

MariaDB Error 1701 occurs when you attempt to use the `TRUNCATE TABLE` statement on a table that is referenced by an existing foreign key constraint in another table. This operation is blocked to prevent data inconsistency, as `TRUNCATE` bypasses row-by-row deletion and does not check foreign key constraints.

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Error Message

Cannot truncate a table referenced in a foreign key constraint (%s)

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Known Causes

3 known causes

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Truncating a Parent Table

You are attempting to truncate a table that acts as the parent in a foreign key relationship, meaning other tables refer to its primary key values.

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Existing Foreign Key Constraint

The target table has one or more foreign key constraints defined on it by other tables, preventing a non-transactional deletion of all its rows.

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Incorrect Statement Usage

`TRUNCATE TABLE` is used, which is a DDL operation that resets the table quickly but does not invoke foreign key actions, unlike `DELETE FROM`.

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Solutions

3 solutions available

1. Temporarily Disable Foreign Key Checks easy

Disable foreign key checks to allow truncation, then re-enable them.

1

Start a MariaDB client session.

2

Disable foreign key checks for the current session.

SET foreign_key_checks = 0;

3

Truncate the table that is causing the error.

TRUNCATE TABLE your_table_name;

4

Re-enable foreign key checks.

SET foreign_key_checks = 1;

2. Drop and Recreate Foreign Key Constraints medium

Identify and drop the offending foreign key, truncate, then recreate the constraint.

1

Identify the foreign key constraint causing the issue. You can do this by querying the `INFORMATION_SCHEMA.KEY_COLUMN_USAGE` table.

SELECT TABLE_NAME, COLUMN_NAME, REFERENCED_TABLE_NAME, REFERENCED_COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_NAME = 'your_table_name' AND CONSTRAINT_SCHEMA = DATABASE();

2

Once identified, drop the foreign key constraint from the referencing table. Replace `constraint_name` with the actual name of the constraint found in the previous step.

ALTER TABLE referencing_table_name DROP FOREIGN KEY constraint_name;

3

Truncate the table.

TRUNCATE TABLE your_table_name;

4

Recreate the foreign key constraint. This requires knowing the original definition of the constraint.

ALTER TABLE referencing_table_name ADD CONSTRAINT constraint_name FOREIGN KEY (column_name) REFERENCES your_table_name (referenced_column_name);

3. Delete Data Instead of Truncating easy

Use DELETE statements to remove data, which respects foreign key constraints.

1

Identify the tables that have foreign key constraints referencing the table you intend to clear. The error message will indicate the referencing table.

2

Delete all rows from the referencing tables that point to the table you want to clear. You may need to perform deletions in a specific order if there are multiple levels of foreign keys.

DELETE FROM referencing_table_name WHERE column_name IN (SELECT column_name FROM your_table_name);

3

Once the referencing tables are cleared, you can then truncate or delete from the target table.

TRUNCATE TABLE your_table_name;

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Related Errors

5 related errors

MariaDB Error 1701: Cannot Truncate Foreign Key Table