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Description

This error occurs when a `VALUES` clause in a MySQL query defines a row with no columns. MySQL requires each row within a `VALUES` clause to contain at least one value, unless it is used specifically as a source for an `INSERT` statement where an empty `VALUES()` can imply default values. This often arises in subqueries or `SELECT` statements.

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Error Message

Each row of a VALUES clause must have at least one column, unless when used as source in an INSERT statement.

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Known Causes

3 known causes

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Empty Row Definition

A `VALUES` clause attempts to define a row with an empty set of parentheses, such as `(VALUES ())` in a context where columns are expected.

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Incorrect Subquery Usage

Using an empty `VALUES()` in a subquery or derived table context where MySQL expects explicit columns to be provided.

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Typographical Error

An accidental omission of column values within a row of a `VALUES` clause during manual SQL composition or programmatic generation.

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Solutions

4 solutions available

1. Correct Syntax for VALUES Clause easy

Ensure each row in a VALUES clause has at least one value specified.

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When using the `VALUES` clause for `INSERT` statements, each set of parentheses must contain at least one value, even if it's `NULL` or an empty string, unless you are inserting into a table with no columns (which is highly unusual and generally not recommended). Review your `INSERT` statement and verify that each row within the `VALUES` clause has a corresponding value for each column you are inserting into, or at least a placeholder like `NULL`.

/* Incorrect syntax: */
INSERT INTO my_table (column1, column2) VALUES ();

/* Correct syntax: */
INSERT INTO my_table (column1, column2) VALUES (NULL, NULL);
-- OR
INSERT INTO my_table (column1, column2) VALUES ('value1', 'value2');

2. Provide Default or NULL Values for Empty Columns easy

Explicitly provide `NULL` or default values for columns when no data is intended.

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If a column in your `INSERT` statement is intended to be empty for a particular row, explicitly specify `NULL` or the column's default value. This error often arises when a set of parentheses in the `VALUES` clause is empty, implying no values are being provided for any columns, which is not allowed unless the table itself has no columns.

/* Assuming 'optional_column' can be empty */
INSERT INTO my_table (column1, column2, optional_column)
VALUES ('some_value', 123, NULL); -- Explicitly use NULL

/* Or if the column has a default value */
INSERT INTO my_table (column1, column2)
VALUES ('another_value', 456); -- If optional_column has a default, it will be used

3. Verify INSERT Statement Structure with Multiple Rows medium

Ensure correct formatting when inserting multiple rows with the VALUES clause.

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When inserting multiple rows using the `VALUES` clause, each row (i.e., each set of parentheses) must be correctly formed and contain the appropriate number of values corresponding to the columns being inserted. An empty `()` pair within the comma-separated list of rows will trigger this error.

/* Incorrect syntax for multiple rows: */
INSERT INTO my_table (col_a, col_b)
VALUES
('row1_a', 'row1_b'),
(), -- This empty row causes the error
('row3_a', 'row3_b');

/* Correct syntax for multiple rows: */
INSERT INTO my_table (col_a, col_b)
VALUES
('row1_a', 'row1_b'),
(NULL, NULL), -- Provide NULL for an empty row
('row3_a', 'row3_b');

4. Check for Empty VALUES Clause in Dynamic SQL Generation advanced

Review code that dynamically generates SQL to prevent empty VALUES clauses.

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If you are generating `INSERT` statements programmatically (e.g., in a scripting language like Python, PHP, or a stored procedure), carefully inspect the logic that constructs the `VALUES` clause. Ensure that no part of your code generates an empty `()` for a row. This might involve checking if data exists for a column before adding it to the values list, and if not, ensuring `NULL` or a placeholder is added instead of nothing.

/* Example in Python (conceptual) */
def generate_insert_sql(data):
    columns = ['col1', 'col2']
    values_list = []
    for row_data in data:
        row_values = []
        for col in columns:
            value = row_data.get(col) # Get value, could be None
            if value is None:
                row_values.append('NULL') # Explicitly add NULL
            else:
                row_values.append(f"'{value}'") # Add string value
        if not row_values: # This check is crucial
            # Handle the case where a row might be empty, but this scenario is rare
            # for INSERT statements expecting columns. Typically, you'd ensure at least one value.
            # For this error, you'd want to avoid generating an empty row entirely.
            pass # Or raise an error, or add a default row
        else:
            values_list.append(f"({','.join(row_values)})")

    if not values_list:
        return "/* No data to insert */"

    return f"INSERT INTO my_table ({','.join(columns)}) VALUES {','.join(values_list)};"

# Example usage:
# data_to_insert = [{'col1': 'A'}, {'col2': 100}] # This would be problematic if not handled
# print(generate_insert_sql(data_to_insert))

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Related Errors

5 related errors

MySQL Error 3942: Empty VALUES Clause Rows