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Description

This error occurs when you attempt to define a `CHECK` constraint on a specific column, but the condition within that constraint refers to a different column within the same table. MySQL's column-level `CHECK` constraints are designed to validate only the column they are defined on, not other columns in the row.

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Error Message

Column check constraint '%s' references other column.

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Known Causes

3 known causes

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Incorrect Constraint Placement

A `CHECK` constraint was defined at the column level, but its condition includes a reference to another column, which is not permitted for column-level constraints.

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Misunderstanding of Constraint Scope

The user intended to create a multi-column validation rule but incorrectly applied it as a column-level `CHECK` constraint, which is strictly limited to the column it's defined on.

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Attempting Cross-Column Validation

An attempt was made to enforce a relationship or comparison between two different columns using a `CHECK` constraint attached to only one of them, leading to this error.

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Solutions

3 solutions available

1. Remove Cross-Column References from Check Constraints easy

Modify the check constraint to only reference the column it's defined on.

1

Identify the check constraint causing the error. This is usually provided in the error message itself.

2

Drop the existing check constraint.

ALTER TABLE your_table_name DROP CONSTRAINT constraint_name;

3

Recreate the check constraint, ensuring it only references the column it's associated with. If the logic requires comparing columns, consider alternative approaches (see other solutions).

ALTER TABLE your_table_name ADD CONSTRAINT new_constraint_name CHECK (your_column_name > 0);

2. Implement Logic in Application Layer or Triggers medium

Move the cross-column validation logic from the check constraint to your application code or a MySQL trigger.

1

Remove the offending check constraint from the table.

ALTER TABLE your_table_name DROP CONSTRAINT constraint_name;

2

In your application code (e.g., Python, Java, PHP), before inserting or updating data, add validation logic that checks the relationship between the columns.

if data['column_a'] <= data['column_b']:
    raise ValueError('Column A must be greater than Column B')

3

Alternatively, create a BEFORE INSERT or BEFORE UPDATE trigger in MySQL to enforce the cross-column logic. The trigger will raise an error if the condition is not met.

DELIMITER //
CREATE TRIGGER enforce_column_relation
BEFORE INSERT ON your_table_name
FOR EACH ROW
BEGIN
    IF NEW.column_a <= NEW.column_b THEN
        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Column A must be greater than Column B';
    END IF;
END;//
DELIMITER ;

3. Use Generated Columns for Derived Values medium

If the check constraint is meant to ensure a relationship that can be derived, use generated columns.

1

Identify the relationship that the check constraint was trying to enforce. For example, if `column_c` should always be `column_a + column_b`.

2

Remove the check constraint that references other columns.

ALTER TABLE your_table_name DROP CONSTRAINT constraint_name;

3

Add a generated column that automatically calculates the derived value. You can then add a check constraint on this generated column if needed.

ALTER TABLE your_table_name ADD COLUMN derived_column INT AS (column_a + column_b) STORED;
ALTER TABLE your_table_name ADD CONSTRAINT check_derived_value CHECK (derived_column > 0);

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Related Errors

5 related errors

MySQL Error 3813: Column Check Constraint References Other Column