I require a code that can validate the presence of an ID in one table and eliminate data from another table if there is no corresponding entry in the first one. In the scenario where users have their IDs stored in one database and their comments in a separate database, if a user is deleted, an efficient script should automatically detect the absence of their ID in the first table and erase all records of their comments in the second table.

Setting up relationships between tables by implementing foreign keys can eliminate the need for a separate script to delete related data when a record is erased from the main table. Unless additional actions such as deleting files are required prior to deletion, manual deletion should suffice. Google provides an example that can be modified to suit your needs.

One effective way to maintain data integrity is to establish relationships between tables using foreign keys with ON DELETE CASCADE. This ensures that data is automatically deleted from any associated tables thereby avoiding potential errors and saving time. However, it is important to consider specific requirements when writing scripts for data management.

DELETE FROM table1 AS t1 WHERE t1.id NOT IN (SELECT t2.id_s FROM table2 AS t2)