The error you’re encountering is due to the incorrect syntax used for adding a default constraint in MySQL. MySQL does not support the DEFAULT keyword for constraints in the same way as some other databases like SQL Server. Instead, you should use the ALTER TABLE statement to add a default value directly to the column definition itself, not as a separate constraint.

Here’s how you can modify your SQL statements to set a default value for the column siUpperAge in the toys table:

Option 1: Add Default Value Directly to Column

If you want to set a default value of 1 for the column siUpperAge, you can modify the column definition directly:

ALTER TABLE toys
MODIFY COLUMN siUpperAge INT DEFAULT 1;

This statement modifies the column definition of siUpperAge in the toys table to set 1 as the default value for new rows.

Option 2: Add Default Value Using ALTER TABLE with CHANGE COLUMN

Alternatively, if the column already exists and you want to add a default value:

ALTER TABLE toys
ALTER COLUMN siUpperAge SET DEFAULT 1;

This statement changes the default value for the siUpperAge column to 1 in the toys table.

Notes:

1. Syntax Differences: MySQL syntax for altering tables and columns is specific and doesn’t use DEFAULT for constraints like SQL Server does.

2. Default Values: If you need to ensure that existing rows get the default value (1 in this case), you might need to update existing rows manually after altering the table structure.

3. Constraints: MySQL supports constraints like PRIMARY KEY, FOREIGN KEY, and UNIQUE in the ALTER TABLE statement, but not DEFAULT as a separate constraint for columns.

By using one of these corrected syntax examples, you should be able to successfully set a default value for the siUpperAge column in your toys table in MySQL. Adjust the statements based on your specific requirements and MySQL version compatibility.