How do I see all foreign keys to a table or column?

Question

In MySQL, how do I get a list of all foreign key constraints pointing to a particular table? a particular column? This is the same thing as this Oracle question, but for MySQL.

Answer 1

If you use InnoDB and defined FK's you could query the information_schema database e.g.:

SELECT * FROM information_schema.TABLE_CONSTRAINTS 
WHERE information_schema.TABLE_CONSTRAINTS.CONSTRAINT_TYPE = 'FOREIGN KEY' 
AND information_schema.TABLE_CONSTRAINTS.TABLE_SCHEMA = 'myschema'
AND information_schema.TABLE_CONSTRAINTS.TABLE_NAME = 'mytable';

Answer 2

Take a look at INFORMATION_SCHEMA.TABLE_CONSTRAINTS, as described here.

Answer 3

The solution I came up with is fragile; it relies on django's naming convention for foreign keys.

USE information_schema;
tee mysql_output
SELECT * FROM TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE = 'FOREIGN KEY' AND TABLE_SCHEMA = 'database_name';
notee

Then, in the shell,

grep 'refs_tablename_id' mysql_output

Answer 4

For a table

use INFORMATION_SCHEMA;

select TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME,
REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME from KEY_COLUMN_USAGE where
REFERENCED_TABLE_NAME = '<table>';

for a column, the same but add an and for the REFERENCED_COLUMN_NAME.