The table schema defines a generated column that references another generated column not yet declared, violating MySQL ordering rules.
ER_GENERATED_COLUMN_NON_PRIOR appears when a generated column refers to another generated column defined later in the CREATE TABLE or ALTER TABLE statement. Reorder the columns so every referenced generated column is declared first, then rerun your DDL.
ER_GENERATED_COLUMN_NON_PRIOR
Error 3107 occurs when a generated column references another generated column that has not yet been declared earlier in the CREATE TABLE or ALTER TABLE statement. MySQL requires any generated column to rely only on columns - generated or not - that are already defined.
The rule was introduced in MySQL 5.7.6 to guarantee deterministic evaluation order. Breaking this rule stops the DDL with SQLSTATE HY000 and the ER_GENERATED_COLUMN_NON_PRIOR message.
The primary cause is column ordering. If col_B is defined as a generated column that depends on col_A, col_A must appear first in the statement. Reversing the order triggers the error.
Copy-pasting table definitions, refactoring schemas, or adding new generated columns with ALTER TABLE often introduces the mis-ordering.
Reorder the generated columns so that every referenced column is declared earlier. The fix may require recreating the table or using ALTER TABLE .. MODIFY .. AFTER syntax.
Always test the adjusted DDL in a staging database to avoid accidental data loss.
During rapid prototyping, developers often append new generated columns at the end. If those columns reference earlier generated columns, no error occurs. If earlier columns start referencing later ones after a refactor, Error 3107 appears. Reorder the columns.
When converting computed columns from other databases, maintain their dependency order or split the change into multiple ALTER steps.
Document column dependencies in comments and maintain clear ordering in version control. Use Galaxy’s SQL editor linting to highlight dependency issues before execution.
Automate schema reviews in CI pipelines so any mis-ordered generated column fails early, not in production.
Error 3106 ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED arises when forbidden functions are used inside a generated column. Replace the function or switch to BEFORE triggers.
Error 3105 ER_INVALID_JSON_PATH_INVALID_DATA_TYPE appears if a JSON path expression inside a generated column targets an invalid type. Validate the JSON structure first.
Generated column defined before the generated column it references.
ALTER TABLE adds a new generated column that depends on one appended later in the same statement.
Schema export tools reorder columns alphabetically, breaking dependency order.
Raised when disallowed functions appear inside a generated column expression.
Occurs when the JSON path expression in a generated column targets an incompatible data type.
Appears if a generated column refers to a non-existent base column due to typos or refactors.
No. MySQL enforces the rule to guarantee evaluation order and query determinism.
Yes. Both virtual and stored generated columns must follow dependency ordering.
Altering column order does not modify data values, but always back up before structural changes.
Galaxy’s editor shows dependency hints and lets you preview DDL, preventing mis-ordered generated columns before execution.
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