Question

I am creating a class which, takes a table from a database, and displays it to a web-page, with as much functionality as possible. One of the things I would like to support, would be having the class detect which columns in the table have a foreign key constraint on them, so that it can then go to those tables, get all of their values and use them in a select-box which is called when you edit those fields, to avoid someone violating foreign key constraints,

The main problem is discovering which fields have a foreign key constraint on them, and which tables they are pointing to. Does anyone know how to do this???

Thanks,

Lemiant

Answer 1

Simple way to get foreign keys for given table:

SELECT
    `column_name`, 
    `referenced_table_schema` AS foreign_db, 
    `referenced_table_name` AS foreign_table, 
    `referenced_column_name`  AS foreign_column 
FROM
    `information_schema`.`KEY_COLUMN_USAGE`
WHERE
    `constraint_schema` = SCHEMA()
AND
    `table_name` = 'your-table-name-here'
AND
    `referenced_column_name` IS NOT NULL
ORDER BY
    `column_name`;