Hey there! Let's sort out that syntax error you're hitting with your ALTER TABLE query. The root issue here is that MySQL requires each separate modification in a single ALTER TABLE statement to be explicitly prefixed with the appropriate keyword—you can't just list indexes or constraints right after adding a column without telling MySQL what action to take for those items.

What Was Wrong in Your Original Query? #

Your original statement tried to add a column, index, and constraint in one go, but skipped the ADD keyword for the index and constraint. MySQL doesn't recognize those as valid operations without that prefix, hence the 1064 syntax error.

Corrected SQL Statement #

Here's the fixed version of your query, with proper syntax for multiple ALTER operations:

ALTER TABLE `booking` 
ADD `feedback_id` INT(11) UNSIGNED NULL, -- Adjust NULL/NOT NULL based on your business needs
ADD INDEX `b_feedback_fk_idx` (`feedback_id` ASC),
ADD CONSTRAINT `feedback_fk` FOREIGN KEY (`feedback_id`) 
REFERENCES `feedback`(`id`);

Key Fixes & Additional Notes: #

• Added ADD before both the index and constraint definitions to clarify each operation for MySQL.
• Explicitly included NULL for the feedback_id column (you can change this to NOT NULL if every booking must be linked to a feedback entry).
• Make sure the id column in your feedback table matches the data type of feedback_id (i.e., it should also be INT(11) UNSIGNED). Mismatched data types will throw another error even after fixing the syntax.
• Verify that feedback.id is either the primary key of the feedback table or has a unique index—MySQL requires foreign keys to reference unique columns.

内容的提问来源于stack exchange，提问作者Jahangir Shah Rashdi