How can I get the foreign keys of a table in mysql

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,

Answer 1

Much can be retrieved from MySQL's information_schema, foreign keys included, as pointed out by dev-null-dweller.

1

SELECT * FROM information_schema.table_constraints 
         WHERE table_schema = 'dbname' AND table_name='mytable';

Instead of dbname use the function SCHEMA() to set the name of the database in USE.

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2

As pointed out by Dan Grossman, the command

SHOW CREATE TABLE `yourtablename`

can be used basically get an SQL dump of the create table statement.

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~3

MySQL provides a SHOW KEYS command. As such you could theoretically get the FK if you know a lower cardinality threshold and have few other keys in the table.

SHOW KEYS FROM `address` WHERE Non_unique AND CARDINALITY > 10000

As the key's cardinality changes each time the internal database is changed, this is rather theoretical. See the cardinality change for instance with running ANALYZE TABLE.

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~4

It is useful to stick to a naming schema, such as foreigntablename_foreignfieldname. For example the field user_id in a table billing. Several ORMs of big Web Content Frameworks use this schema.