Error
Error Code:
3764
MySQL Error 3764: Generated Column Dependency Invalid
Description
This error occurs when defining a generated column whose expression attempts to reference a row value in an invalid context. Most commonly, it signifies that a generated column's expression is trying to directly refer to another generated column within the same table, which MySQL explicitly disallows.
Error Message
Expression of generated column '%s' cannot refer to a row value.
Known Causes
3 known causesReferencing Another Generated Column
The expression for a generated column attempts to use the value of another column that is also defined as a generated column in the same table.
Circular Dependency Among Generated Columns
Two or more generated columns are defined in a way that creates a circular reference, where each column's expression depends on another generated column that eventually depends back on the first.
Invalid Self-Reference in Expression
The generated column's expression attempts to refer to itself or to a value that is not yet stable during its own computation.
Solutions
3 solutions available1. Modify Generated Column Expression to Use Other Columns easy
Rewrite the generated column's expression to reference only other columns and not the entire row.
1
Identify the generated column causing the error. The error message will specify its name (e.g., `generated_column_name`).
2
Examine the `CREATE TABLE` or `ALTER TABLE` statement for the generated column. Locate the `AS (expression)` part.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (your_expression);3
Modify the `expression` to reference only specific columns. For example, if the expression was `AS (ROW())`, change it to `AS (column1 + column2)` or `AS (column1)`.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (column1 + column2);4
Re-apply the `ALTER TABLE` statement to update the table definition.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (column1 + column2);2. Remove or Redesign the Generated Column medium
If the generated column's logic cannot be expressed using individual columns, consider removing it or redesigning the table.
1
Determine if the generated column is essential for your application's functionality.
2
If not essential, drop the generated column using `ALTER TABLE`.
ALTER TABLE your_table DROP COLUMN generated_column_name;3
If essential, re-evaluate your table design. You might need to calculate this value in your application logic or use a different approach that doesn't rely on row-level references within a generated column expression.
3. Ensure Generated Column References are Valid Column Names easy
Verify that the expression in the generated column correctly refers to existing columns and not reserved keywords or invalid expressions.
1
List all columns in your table to confirm their names.
SHOW COLUMNS FROM your_table;2
Carefully review the expression for your generated column in the `CREATE TABLE` or `ALTER TABLE` statement.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (your_expression);3
Ensure that every identifier within `your_expression` corresponds to a valid column name in `your_table`. Avoid using expressions like `ROW()` or functions that implicitly operate on the entire row in a way that MySQL interprets as a disallowed reference.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (column_a * column_b);4
Correct any typos or incorrect column references and re-apply the `ALTER TABLE` statement.
ALTER TABLE your_table MODIFY COLUMN generated_column_name INT AS (corrected_column_a * corrected_column_b);