I have tables that I've tried setting PK FK relationships on but I want to verify this. How can I show the PK/FK restraints? I saw this manual page, but it does not show examples and my google search was fruitless also. My database is credentialing1
and my constrained tables are practices
and cred_insurances
.
254
votes
8 Answers
458
votes
127
votes
21
votes
The main problem with the validated answer is you'll have to parse the output to get the informations. Here is a query allowing you to get them in a more usable manner :
SELECT cols.TABLE_NAME, cols.COLUMN_NAME, cols.ORDINAL_POSITION,
cols.COLUMN_DEFAULT, cols.IS_NULLABLE, cols.DATA_TYPE,
cols.CHARACTER_MAXIMUM_LENGTH, cols.CHARACTER_OCTET_LENGTH,
cols.NUMERIC_PRECISION, cols.NUMERIC_SCALE,
cols.COLUMN_TYPE, cols.COLUMN_KEY, cols.EXTRA,
cols.COLUMN_COMMENT, refs.REFERENCED_TABLE_NAME, refs.REFERENCED_COLUMN_NAME,
cRefs.UPDATE_RULE, cRefs.DELETE_RULE,
links.TABLE_NAME, links.COLUMN_NAME,
cLinks.UPDATE_RULE, cLinks.DELETE_RULE
FROM INFORMATION_SCHEMA.`COLUMNS` as cols
LEFT JOIN INFORMATION_SCHEMA.`KEY_COLUMN_USAGE` AS refs
ON refs.TABLE_SCHEMA=cols.TABLE_SCHEMA
AND refs.REFERENCED_TABLE_SCHEMA=cols.TABLE_SCHEMA
AND refs.TABLE_NAME=cols.TABLE_NAME
AND refs.COLUMN_NAME=cols.COLUMN_NAME
LEFT JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS cRefs
ON cRefs.CONSTRAINT_SCHEMA=cols.TABLE_SCHEMA
AND cRefs.CONSTRAINT_NAME=refs.CONSTRAINT_NAME
LEFT JOIN INFORMATION_SCHEMA.`KEY_COLUMN_USAGE` AS links
ON links.TABLE_SCHEMA=cols.TABLE_SCHEMA
AND links.REFERENCED_TABLE_SCHEMA=cols.TABLE_SCHEMA
AND links.REFERENCED_TABLE_NAME=cols.TABLE_NAME
AND links.REFERENCED_COLUMN_NAME=cols.COLUMN_NAME
LEFT JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS cLinks
ON cLinks.CONSTRAINT_SCHEMA=cols.TABLE_SCHEMA
AND cLinks.CONSTRAINT_NAME=links.CONSTRAINT_NAME
WHERE cols.TABLE_SCHEMA=DATABASE()
AND cols.TABLE_NAME="table"
13
votes
7
votes
6
votes
You can use this:
select
table_name,column_name,referenced_table_name,referenced_column_name
from
information_schema.key_column_usage
where
referenced_table_name is not null
and table_schema = 'my_database'
and table_name = 'my_table'
Or for better formatted output use this:
select
concat(table_name, '.', column_name) as 'foreign key',
concat(referenced_table_name, '.', referenced_column_name) as 'references'
from
information_schema.key_column_usage
where
referenced_table_name is not null
and table_schema = 'my_database'
and table_name = 'my_table'
1
votes
Analogous to @Resh32, but without the need to use the USE
statement:
SELECT TABLE_NAME,
COLUMN_NAME,
CONSTRAINT_NAME,
REFERENCED_TABLE_NAME,
REFERENCED_COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE TABLE_SCHEMA = "database_name"
AND TABLE_NAME = "table_name"
AND REFERENCED_COLUMN_NAME IS NOT NULL;
Useful, e.g. using the ORM.
0
votes
There is also a tool that oracle made called mysqlshow
If you run it with the --k keys $table_name
option it will display the keys.
SYNOPSIS
mysqlshow [options] [db_name [tbl_name [col_name]]]
.......
.......
.......
· --keys, -k
Show table indexes.
example:
╰─➤ mysqlshow -h 127.0.0.1 -u root -p --keys database tokens
Database: database Table: tokens
+-----------------+------------------+--------------------+------+-----+---------+----------------+---------------------------------+---------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+-----------------+------------------+--------------------+------+-----+---------+----------------+---------------------------------+---------+
| id | int(10) unsigned | | NO | PRI | | auto_increment | select,insert,update,references | |
| token | text | utf8mb4_unicode_ci | NO | | | | select,insert,update,references | |
| user_id | int(10) unsigned | | NO | MUL | | | select,insert,update,references | |
| expires_in | datetime | | YES | | | | select,insert,update,references | |
| created_at | timestamp | | YES | | | | select,insert,update,references | |
| updated_at | timestamp | | YES | | | | select,insert,update,references | |
+-----------------+------------------+--------------------+------+-----+---------+----------------+---------------------------------+---------+
+--------+------------+--------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+--------+------------+--------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| tokens | 0 | PRIMARY | 1 | id | A | 2 | | | | BTREE | | |
| tokens | 1 | tokens_user_id_foreign | 1 | user_id | A | 2 | | | | BTREE | | |
+--------+------------+--------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+