我有表,我已经尝试设置PK FK关系,但我想验证这一点。如何显示PK/FK约束?我看到了这个手册页,但它没有显示示例,我的谷歌搜索也是徒劳的。我的数据库是credentialing1,约束表是practices和cred_insurances。
我使用
SHOW CREATE TABLE mytable;
这向您展示了以当前形式重新创建mytable所需的SQL语句。您可以看到所有的列及其类型(如DESC),但它还显示约束信息(以及表类型、字符集等)。
简单地查询INFORMATION_SCHEMA:
USE INFORMATION_SCHEMA;
SELECT TABLE_NAME,
COLUMN_NAME,
CONSTRAINT_NAME,
REFERENCED_TABLE_NAME,
REFERENCED_COLUMN_NAME
FROM KEY_COLUMN_USAGE
WHERE TABLE_SCHEMA = "<your_database_name>"
AND TABLE_NAME = "<your_table_name>"
AND REFERENCED_COLUMN_NAME IS NOT NULL;
你可以用这个:
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'
或者为了更好的格式输出使用:
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'
经过验证的答案的主要问题是必须解析输出以获得信息。下面是一个查询,允许您以更有用的方式获取它们:
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"
如果要向information_schema请求,你需要特权。如果你需要简单的键列表,你可以使用这个命令:
SHOW INDEXES IN <tablename>
还有一个oracle做的工具叫mysqlshow
如果你使用——k keys $table_name选项运行它,它将显示键。
SYNOPSIS
mysqlshow [options] [db_name [tbl_name [col_name]]]
.......
.......
.......
· --keys, -k
Show table indexes.
例子:
╰─➤ 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 | | |
+--------+------------+--------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
类似于@Resh32,但是不需要使用use语句:
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;
有用,例如使用ORM。