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Description

MariaDB Error 1825 indicates that the database encountered an issue when attempting to add a foreign key constraint to a table. This typically occurs when the `FOREIGN KEY` definition includes options or clauses that are either syntactically incorrect, not supported by the current MariaDB version, or conflict with other table or column properties.

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Error Message

Failed to add the foreign key constraint on table '%s'. Incorrect options in FOREIGN KEY constraint '%s'

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Known Causes

4 known causes

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Unsupported ON DELETE/UPDATE Action

The `ON DELETE` or `ON UPDATE` clause specifies an action (e.g., `SET NULL`, `CASCADE`) that is not supported for the given foreign key definition or related tables in your MariaDB version.

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Invalid Constraint Attributes

The foreign key definition includes attributes like `MATCH FULL`, `MATCH PARTIAL`, or `MATCH SIMPLE` that are either not recognized or incorrectly applied in the current MariaDB version or context.

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Incorrectly Formatted Syntax

There are syntax errors in the foreign key definition, such as misspelled keywords, missing commas, or incorrect parentheses, preventing the database from parsing the constraint options correctly.

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Conflicting or Redundant Options

The foreign key definition contains options that conflict with each other or are redundant, leading to an ambiguous or invalid constraint specification that MariaDB cannot process.

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Solutions

3 solutions available

1. Correct Foreign Key Syntax and Options easy

Ensures the FOREIGN KEY syntax and associated options are valid according to MariaDB standards.

1

Review the `CREATE TABLE` or `ALTER TABLE` statement where the foreign key is defined. Pay close attention to the `FOREIGN KEY` clause and its options.

2

Verify that you are using valid `ON DELETE` and `ON UPDATE` actions. Allowed values include `RESTRICT`, `CASCADE`, `SET NULL`, `NO ACTION` (which is equivalent to `RESTRICT` in MariaDB), and `SET DEFAULT` (for specific storage engines).

Example of correct syntax:

sql
CREATE TABLE child_table (
    id INT PRIMARY KEY,
    parent_id INT,
    FOREIGN KEY (parent_id)
        REFERENCES parent_table(id)
        ON DELETE CASCADE
        ON UPDATE RESTRICT
);

3

Ensure that the referenced columns in the `REFERENCES` clause are part of a `PRIMARY KEY` or have a `UNIQUE` index on the parent table. If they are not, you'll need to create such an index first.

Example: Add a unique index to the parent table if needed.

sql
ALTER TABLE parent_table ADD UNIQUE INDEX unique_parent_id (id);

4

If you're using `MATCH FULL` or `MATCH PARTIAL`, ensure your storage engine supports these options. `MATCH SIMPLE` is the default and most widely supported.

2. Check Data Type and Collation Consistency medium

Ensures that the data types and character set/collation of the foreign key columns match between the referencing and referenced tables.

1

Identify the columns involved in the foreign key constraint (both in the referencing and referenced tables).

2

Use `DESCRIBE` or `SHOW CREATE TABLE` to inspect the data types, character sets, and collations of these columns in both tables.

sql
DESCRIBE referencing_table;
DESCRIBE referenced_table;


OR

sql
SHOW CREATE TABLE referencing_table;
SHOW CREATE TABLE referenced_table;

3

Modify the data types, character sets, or collations of the columns in the referencing table to exactly match those in the referenced table. This is crucial for foreign key enforcement.

Example: If `referencing_table.parent_id` is `INT UNSIGNED` and `referenced_table.id` is `INT`, change `referencing_table.parent_id` to `INT`.

sql
ALTER TABLE referencing_table MODIFY COLUMN parent_id INT;

3. Recreate the Foreign Key Constraint medium

Removes and then re-adds the foreign key constraint to resolve potential inconsistencies or syntax errors.

1

Identify the name of the foreign key constraint that is causing the error. This is usually provided in the error message.

2

Drop the existing foreign key constraint from the referencing table.

sql
ALTER TABLE referencing_table DROP FOREIGN KEY constraint_name;

3

Re-add the foreign key constraint with the correct syntax and options. Ensure you are using valid `ON DELETE` and `ON UPDATE` actions, and that the referenced columns are indexed.

sql
ALTER TABLE referencing_table ADD CONSTRAINT constraint_name
    FOREIGN KEY (referencing_column)
    REFERENCES referenced_table(referenced_column)
    ON DELETE CASCADE
    ON UPDATE RESTRICT;

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Related Errors

5 related errors

MariaDB Error 1825: Invalid Foreign Key Constraint Options