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Description

This error indicates an incorrect usage of the `DEFAULT` function within a context where a `DEFAULT` value expression is expected, such as in a column definition. It typically arises when attempting to define a column's default or working with generated columns in a way that conflicts with MySQL's syntax rules.

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Error Message

DEFAULT function cannot be used with default value expressions

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Known Causes

3 known causes

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DEFAULT() in Column Definition

Attempting to use the `DEFAULT(column_name)` function directly within a `DEFAULT` clause when defining a column's default value in `CREATE TABLE` or `ALTER TABLE` statements.

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Confusing DEFAULT Keyword and Function

Mistaking the `DEFAULT` keyword, which specifies a literal value or expression for a column's default, with the `DEFAULT()` function, which is used to retrieve an existing default value.

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DEFAULT() in Generated Column Expressions

Including the `DEFAULT()` function as part of the expression for a generated column or a column whose default value is derived from a complex expression.

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Solutions

3 solutions available

1. Explicitly Define Default Values easy

Replace the `DEFAULT` keyword with the actual default value expression.

1

Identify the column definition causing the error. It will look something like `column_name datatype DEFAULT (expression)`.

2

Remove the `DEFAULT` keyword and directly specify the expression as the default value. For example, change `DEFAULT (CURRENT_TIMESTAMP)` to `DEFAULT CURRENT_TIMESTAMP` or `DEFAULT 'N/A'`.

ALTER TABLE your_table MODIFY COLUMN your_column datatype DEFAULT expression;

3

If you are creating a new table, ensure you are not using `DEFAULT` with expressions in the column definition. Instead, provide the expression directly.

CREATE TABLE your_table (
    your_column datatype DEFAULT expression
);

2. Utilize `GENERATED` Columns for Complex Defaults medium

For complex default calculations, use generated columns instead of traditional `DEFAULT` clauses.

1

If the 'default value' is derived from other columns or requires complex logic, it's better to define it as a generated column.

2

Remove the problematic `DEFAULT` clause from the column definition.

ALTER TABLE your_table DROP DEFAULT FROM your_column;

3

Add a new generated column that calculates the desired value.

ALTER TABLE your_table ADD COLUMN new_calculated_column datatype [STORED | VIRTUAL] AS (expression);

4

If the original column was intended to store this value, you might consider dropping the original column and replacing it with the generated one, or updating the original column's values based on the generated column.

3. Ensure Correct `DEFAULT` Syntax for Literals and Functions easy

Verify that you are using the correct syntax for literal default values and built-in functions.

1

For literal values (strings, numbers, booleans), enclose them in appropriate quotes or use them directly.

CREATE TABLE example (
    status VARCHAR(10) DEFAULT 'active',
    count INT DEFAULT 0
);

2

For built-in functions like `CURRENT_TIMESTAMP`, `UUID()`, `NOW()`, etc., use them directly without the `DEFAULT` keyword followed by parentheses.

CREATE TABLE logs (
    log_id INT AUTO_INCREMENT PRIMARY KEY,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

3

Review the MySQL documentation for the specific function you are trying to use as a default to confirm its correct usage.

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Related Errors

5 related errors

MySQL Error 3773: Misusing DEFAULT with Expressions