How can I solve the issue of “cannot truncate a table referenced in a foreign key constraint?”

 I am assigned a task which is related to cleaning the database by removing some old files from a table whose name is “orders”. However, during the process of truncating the table, I encountered a scenario where an error message occurred which showed “ cannot truncate a table referenced in a foreign key constraint”. Now how can I solve this particular issue? 

Answered by Charles Parr

In the context of web development, If you are getting the error message “cannot truncate a table referenced in a foreign key constraint” then it can be due to because the other tables reference it through foreign key constraints. Here are the steps given to solve this particular issue:-

Identify dependent tables

First, you would need to find the tables that reference the “orders” table by foreign key constraints. Here is an example:-

SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_NAME = ‘orders’;

Drop or disable constraints

Once you can find the dependent tables, now you can either drop or disable the key constraints. For instance:-

To drop a foreign key constraint

        ALTER TABLE dependent_table_name
DROP FOREIGN KEY constraint_name;
To disable constraints
ALTER TABLE dependent_table_name
DISABLE CONSTRAINT constraint_name;

Truncate the table

After completing the process of disabling or dropping, now you can truncate the orders table. Here is what you can:-

  TRUNCATE TABLE orders;


Your Answer

Interviews

Parent Categories